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Transmembrane protein

A transmembrane protein is a type of integral membrane protein that spans the entirety of the cell membrane. Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane. They frequently undergo significant conformational changes to move a substance through the membrane. They are usually highly hydrophobic and aggregate and precipitate in water. They require detergents or nonpolar solvents for extraction, although some of them (beta-barrels) can be also extracted using denaturing agents.

The peptide sequence that spans the membrane, or the transmembrane segment, is largely hydrophobic and can be visualized using the hydropathy plot. Depending on the number of transmembrane segments, transmembrane proteins can be classified as single-pass membrane proteins, or as multipass membrane proteins. Some other integral membrane proteins are called monotopic, meaning that they are also permanently attached to the membrane, but do not pass through it.

Classification by structure
There are two basic types of transmembrane proteins: alpha-helical and beta barrels. Alpha-helical proteins are present in the inner membranes of bacterial cells or the plasma membrane of eukaryotic cells, and sometimes in the bacterial outer membrane. This is the major category of transmembrane proteins. In humans, 27% of all proteins have been estimated to be alpha-helical membrane proteins. Beta-barrel proteins are so far found only in outer membranes of gram-negative bacteria, cell walls of gram-positive bacteria, outer membranes of mitochondria and chloroplasts, or can be secreted as pore-forming toxins. All beta-barrel transmembrane proteins have simplest up-and-down topology, which may reflect their common evolutionary origin and similar folding mechanism.

In addition to the protein domains, there are unusual transmembrane elements formed by peptides. A typical example is gramicidin A, a peptide that forms a dimeric transmembrane β-helix. This peptide is secreted by gram-positive bacteria as an antibiotic. A transmembrane polyproline-II helix has not been reported in natural proteins. Nonetheless, this structure was experimentally observed in specifically designed artificial peptides.

Classification by topology
This classification refers to the position of the protein N- and C-termini on the different sides of the lipid bilayer. Types I, II, III and IV are single-pass molecules. Type I transmembrane proteins are anchored to the lipid membrane with a stop-transfer anchor sequence and have their N-terminal domains targeted to the endoplasmic reticulum (ER) lumen during synthesis (and the extracellular space, if mature forms are located on cell membranes). Type II and III are anchored with a signal-anchor sequence, with type II being targeted to the ER lumen with its C-terminal domain, while type III have their N-terminal domains targeted to the ER lumen. Type IV is subdivided into IV-A, with their N-terminal domains targeted to the cytosol and IV-B, with an N-terminal domain targeted to the lumen. The implications for the division in the four types are especially manifest at the time of translocation and ER-bound translation, when the protein has to be passed through the ER membrane in a direction dependent on the type.

3D structure
Membrane protein structures can be determined by X-ray crystallography, electron microscopy or NMR spectroscopy. The most common tertiary structures of these proteins are transmembrane helix bundle and beta barrel. The portion of the membrane proteins that are attached to the lipid bilayer (see annular lipid shell) consist mostly of hydrophobic amino acids.

Membrane proteins which have hydrophobic surfaces, are relatively flexible and are expressed at relatively low levels. This creates difficulties in obtaining enough protein and then growing crystals. Hence, despite the significant functional importance of membrane proteins, determining atomic resolution structures for these proteins is more difficult than globular proteins. As of January 2013 less than 0.1% of protein structures determined were membrane proteins despite being 20–30% of the total proteome. Due to this difficulty and the importance of this class of proteins methods of protein structure prediction based on hydropathy plots, the positive inside rule and other methods have been developed.

Stability of alpha-helical transmembrane proteins
Transmembrane alpha-helical (α-helical) proteins are unusually stable judging from thermal denaturation studies, because they do not unfold completely within the membranes (the complete unfolding would require breaking down too many α-helical H-bonds in the nonpolar media). On the other hand, these proteins easily misfold, due to non-native aggregation in membranes, transition to the molten globule states, formation of non-native disulfide bonds, or unfolding of peripheral regions and nonregular loops that are locally less stable.

It is also important to properly define the unfolded state. The unfolded state of membrane proteins in detergent micelles is different from that in the thermal denaturation experiments. This state represents a combination of folded hydrophobic α-helices and partially unfolded segments covered by the detergent. For example, the "unfolded" bacteriorhodopsin in SDS micelles has four transmembrane α-helices folded, while the rest of the protein is situated at the micelle-water interface and can adopt different types of non-native amphiphilic structures. Free energy differences between such detergent-denatured and native states are similar to stabilities of water-soluble proteins (< 10 kcal/mol).

Folding of α-helical transmembrane proteins
Refolding of α-helical transmembrane proteins in vitro is technically difficult. There are relatively few examples of the successful refolding experiments, as for bacteriorhodopsin. In vivo, all such proteins are normally folded co-translationally within the large transmembrane translocon. The translocon channel provides a highly heterogeneous environment for the nascent transmembrane α-helices. A relatively polar amphiphilic α-helix can adopt a transmembrane orientation in the translocon (although it would be at the membrane surface or unfolded in vitro), because its polar residues can face the central water-filled channel of the translocon. Such mechanism is necessary for incorporation of polar α-helices into structures of transmembrane proteins. The amphiphilic helices remain attached to the translocon until the protein is completely synthesized and folded. If the protein remains unfolded and attached to the translocon for too long, it is degraded by specific "quality control" cellular systems.

Stability and folding of beta-barrel transmembrane proteins
Stability of beta barrel (β-barrel) transmembrane proteins is similar to stability of water-soluble proteins, based on chemical denaturation studies. Some of them are very stable even in chaotropic agents and high temperature. Their folding in vivo is facilitated by water-soluble chaperones, such as protein Skp. It is thought that β-barrel membrane proteins come from one ancestor even having different number of sheets which could be added or doubled during evolution. Some studies show a huge sequence conservation among different organisms and also conserved amino acids which hold the structure and help with folding.

Light absorption-driven transporters

 * Bacteriorhodopsin-like proteins including rhodopsin (see also opsin)
 * Bacterial photosynthetic reaction centres and photosystems I and II
 * Light-harvesting complexes from bacteria and chloroplasts

Oxidoreduction-driven transporters

 * Transmembrane cytochrome b-like proteins: coenzyme Q - cytochrome c reductase (cytochrome bc1 ); cytochrome b6f complex; formate dehydrogenase, respiratory nitrate reductase; succinate - coenzyme Q reductase (fumarate reductase); and succinate dehydrogenase. See electron transport chain.
 * Cytochrome c oxidases from bacteria and mitochondria

Electrochemical potential-driven transporters

 * Proton or sodium translocating F-type and V-type ATPases

P-P-bond hydrolysis-driven transporters

 * P-type calcium ATPase (five different conformations)
 * Calcium ATPase regulators phospholamban and sarcolipin
 * ABC transporters
 * General secretory pathway (Sec) translocon (preprotein translocase SecY)

Porters (uniporters, symporters, antiporters)

 * Mitochondrial carrier proteins
 * Major Facilitator Superfamily (Glycerol-3-phosphate transporter, Lactose permease, and Multidrug transporter EmrD)
 * Resistance-nodulation-cell division (multidrug efflux transporter AcrB, see multidrug resistance)
 * Dicarboxylate/amino acid:cation symporter (proton glutamate symporter)
 * Monovalent cation/proton antiporter (Sodium/proton antiporter 1 NhaA)
 * Neurotransmitter sodium symporter
 * Ammonia transporters
 * Drug/Metabolite Transporter (small multidrug resistance transporter EmrE - the structures are retracted as erroneous)

Alpha-helical channels including ion channels

 * Voltage-gated ion channel like, including potassium channels KcsA and KvAP, and inward-rectifier potassium ion channel Kirbac
 * Large-conductance mechanosensitive channel, MscL
 * Small-conductance mechanosensitive ion channel (MscS)
 * CorA metal ion transporters
 * Ligand-gated ion channel of neurotransmitter receptors (acetylcholine receptor)
 * Aquaporins
 * Chloride channels
 * Outer membrane auxiliary proteins (polysaccharide transporter) - α-helical transmembrane proteins from the outer bacterial membrane

Enzymes

 * Methane monooxygenase
 * Rhomboid protease
 * Disulfide bond formation protein (DsbA-DsbB complex)

Proteins with single transmembrane alpha-helices

 * Subunits of T cell receptor complex
 * Cytochrome c nitrite reductase complex
 * Glycophorin A dimer
 * Inovirus (filamentous phage) major coat protein
 * Pilin
 * Pulmonary surfactant-associated protein
 * Monoamine oxidases A and B
 * Fatty acid amide hydrolase
 * Cytochrome P450 oxidases
 * Corticosteroid 11β-dehydrogenases.
 * Signal Peptide Peptidase

Beta-barrels composed of a single polypeptide chain

 * Beta barrels from eight beta-strands and with "shear number" of ten (n=8, S=10). They include:
 * OmpA-like transmembrane domain (OmpA)
 * Virulence-related outer membrane protein family (OmpX)
 * Outer membrane protein W family (OmpW)
 * Antimicrobial peptide resistance and lipid A acylation protein family (PagP)
 * Lipid A deacylase PagL
 * Opacity family porins (NspA)
 * Autotransporter domain (n=12,S=14)
 * FadL outer membrane protein transport family, including Fatty acid transporter FadL (n=14,S=14)
 * General bacterial porin family, known as trimeric porins (n=16,S=20)
 * Maltoporin, or sugar porins (n=18,S=22)
 * Nucleoside-specific porin (n=12,S=16)
 * Outer membrane phospholipase A1(n=12,S=16)
 * TonB-dependent receptors and their plug domain. They are ligand-gated outer membrane channels (n=22,S=24), including cobalamin transporter BtuB, Fe(III)-pyochelin receptor FptA, receptor FepA, ferric hydroxamate uptake receptor FhuA, transporter FecA, and pyoverdine receptor FpvA
 * Outer membrane protein OpcA family (n=10,S=12) that includes outer membrane protease OmpT and adhesin/invasin OpcA protein
 * Outer membrane protein G porin family (n=14,S=16)

Note: n and S are, respectively, the number of beta-strands and the "shear number" of the beta-barrel

Beta-barrels composed of several polypeptide chains

 * Trimeric autotransporter (n=12,S=12)
 * Outer membrane efflux proteins, also known as trimeric outer membrane factors (n=12,S=18) including TolC and multidrug resistance proteins
 * MspA porin (octamer, n=S=16) and α-hemolysin (heptamer n=S=14) . These proteins are secreted.

title: Transmembrane protein


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Antiochus IX Cyzicenus

Antiochus IX Eusebes Cyzicenus (, "Antiochus the Pious, the Cyzicene") was a ruler of the Hellenistic Seleucid kingdom. He was the son of Antiochus VII Sidetes and Cleopatra Thea. He left the kingdom in 129 BC and went to the city of Cyzicus, but he returned in 116 BC to challenge his half-brother Antiochus VIII for power.

The siblings fought a twenty-year civil war. In 112 BC, Antiochus IX's wife, Cleopatra IV, was killed by her sister Tryphaena, the wife of Antiochus VIII. Tryphaena herself died shortly afterwards. Antiochus VIII was assassinated in 96 BC; he was succeeded by his sons Seleucus VI and Demetrius III. Antiochus IX then took the capital Antioch and married his deceased wife's sister Cleopatra Selene, who was herself the widow of Antiochus VIII. Seleucus VI continued the war against his uncle. Antiochus IX Eusebes Cyzicenus was killed in battle in 96 B.C.

Biography
The son of Antiochus VII Sidetes and Cleopatra Thea, upon the death of his father in Parthia and his uncle Demetrius II Nicator's return to power (129 BC), his mother sent him to Cyzicus on the Bosporus, thus giving him his nickname.

Following the death of his mother c. 121 BC, Antiochus IX Cyzicenus challenged his half-brother, Antiochus VIII Grypus, for power over Syria.

He returned to Syria in 116 BC to claim the Seleucid throne from his half-brother/cousin Antiochus VIII Grypus, with whom he eventually divided Syria, that same year.

Antiochus IX Cyzicenus was first married to Cleopatra IV, who was said to have been killed in 112 BC by her sister and rival Tryphaena, wife of King Grypus. After the death of Grypus and Antiochus' capture of the capital, Antiochus married Cleopatra Selene of Syria, the sister of his former wife, Cleopatra IV.

He was subsequently killed in battle by the son of Grypus, Seleucus VI Epiphanes, later in 96 BC.

Legacy
Antiochus IX probably created the Iturean tetrarchy as an ally against Antiochus VIII.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Antiochus IX Cyzicenus


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Peripheral membrane protein

Peripheral membrane proteins, or extrinsic membrane proteins, are membrane proteins that adhere only temporarily to the biological membrane with which they are associated. These proteins attach to integral membrane proteins, or penetrate the peripheral regions of the lipid bilayer. The regulatory protein subunits of many ion channels and transmembrane receptors, for example, may be defined as peripheral membrane proteins. In contrast to integral membrane proteins, peripheral membrane proteins tend to collect in the water-soluble component, or fraction, of all the proteins extracted during a protein purification procedure. Proteins with GPI anchors are an exception to this rule and can have purification properties similar to those of integral membrane proteins.

The reversible attachment of proteins to biological membranes has shown to regulate cell signaling and many other important cellular events, through a variety of mechanisms. For example, the close association between many enzymes and biological membranes may bring them into close proximity with their lipid substrate(s). Membrane binding may also promote rearrangement, dissociation, or conformational changes within many protein structural domains, resulting in an activation of their biological activity. Additionally, the positioning of many proteins are localized to either the inner or outer surfaces or leaflets of their resident membrane. This facilitates the assembly of multi-protein complexes by increasing the probability of any appropriate protein–protein interactions.

Binding to the lipid bilayer
Peripheral membrane proteins may interact with other proteins or directly with the lipid bilayer. In the latter case, they are then known as amphitropic proteins. Some proteins, such as G-proteins and certain protein kinases, interact with transmembrane proteins and the lipid bilayer simultaneously. Some polypeptide hormones, antimicrobial peptides, and neurotoxins accumulate at the membrane surface prior to locating and interacting with their cell surface receptor targets, which may themselves be peripheral membrane proteins.

The phospholipid bilayer that forms the cell surface membrane consists of a hydrophobic inner core region sandwiched between two regions of hydrophilicity, one at the inner surface and one at the outer surface of the cell membrane (see lipid bilayer article for a more detailed structural description of the cell membrane). The inner and outer surfaces, or interfacial regions, of model phospholipid bilayers have been shown to have a thickness of around 8 to 10 Å, although this may be wider in biological membranes that include large amounts of gangliosides or lipopolysaccharides. The hydrophobic inner core region of typical biological membranes may have a thickness of around 27 to 32 Å, as estimated by Small angle X-ray scattering (SAXS). The boundary region between the hydrophobic inner core and the hydrophilic interfacial regions is very narrow, at around 3 Å, (see lipid bilayer article for a description of its component chemical groups). Moving outwards away from the hydrophobic core region and into the interfacial hydrophilic region, the effective concentration of water rapidly changes across this boundary layer, from nearly zero to a concentration of around 2 M. The phosphate groups within phospholipid bilayers are fully hydrated or saturated with water and are situated around 5 Å outside the boundary of the hydrophobic core region.

Some water-soluble proteins associate with lipid bilayers irreversibly and can form transmembrane alpha-helical or beta-barrel channels. Such transformations occur in pore forming toxins such as colicin A, alpha-hemolysin, and others. They may also occur in BcL-2 like protein, in some amphiphilic antimicrobial peptides , and in certain annexins. These proteins are usually described as peripheral as one of their conformational states is water-soluble or only loosely associated with a membrane.

Membrane binding mechanisms
The association of a protein with a lipid bilayer may involve significant changes within tertiary structure of a protein. These may include the folding of regions of protein structure that were previously unfolded or a re-arrangement in the folding or a refolding of the membrane-associated part of the proteins. It also may involve the formation or dissociation of protein quaternary structures or oligomeric complexes, and specific binding of ions, ligands, or regulatory lipids.

Typical amphitropic proteins must interact strongly with the lipid bilayer in order to perform their biological functions. These include the enzymatic processing of lipids and other hydrophobic substances, membrane anchoring, and the binding and transfer of small nonpolar compounds between different cellular membranes. These proteins may be anchored to the bilayer as a result of hydrophobic interactions between the bilayer and exposed nonpolar residues at the surface of a protein, by specific non-covalent binding interactions with regulatory lipids, or through their attachment to covalently bound lipid anchors.

It has been shown that the membrane binding affinities of many peripheral proteins depend on the specific lipid composition of the membrane with which they are associated.

Non-specific hydrophobic association
Amphitropic proteins associate with lipid bilayers via various hydrophobic anchor structures. Such as amphiphilic α-helixes, exposed nonpolar loops, post-translationally acylated or lipidated amino acid residues, or acyl chains of specifically bound regulatory lipids such as phosphatidylinositol phosphates. Hydrophobic interactions have been shown to be important even for highly cationic peptides and proteins, such as the polybasic domain of the MARCKS protein or histactophilin, when their natural hydrophobic anchors are present.

Covalently bound lipid anchors
Lipid anchored proteins are covalently attached to different fatty acid acyl chains on the cytoplasmic side of the cell membrane via palmitoylation, myristoylation, or prenylation. On the exoplasmic face of the cell membrane, lipid anchored proteins are covalently attached to the lipids glycosylphosphatidylinositol (GPI) and cholesterol. Protein association with membranes through the use of acylated residues is a reversible process, as the acyl chain can be buried in a protein's hydrophobic binding pocket after dissociation from the membrane. This process occurs within the beta-subunits of G-proteins. Perhaps because of this additional need for structural flexibility, lipid anchors are usually bound to the highly flexible segments of proteins tertiary structure that are not well resolved by protein crystallographic studies.

Specific protein–lipid binding
Some cytosolic proteins are recruited to different cellular membranes by recognizing certain types of lipid found within a given membrane. Binding of a protein to a specific lipid occurs via specific membrane-targeting structural domains that occur within the protein and have specific binding pockets for the lipid head groups of the lipids to which they bind. This is a typical biochemical protein–ligand interaction, and is stabilized by the formation of intermolecular hydrogen bonds, van der Waals interactions, and hydrophobic interactions between the protein and lipid ligand. Such complexes are also stabilized by the formation of ionic bridges between the aspartate or glutamate residues of the protein and lipid phosphates via intervening calcium ions (Ca2+). Such ionic bridges can occur and are stable when ions (such as Ca2+) are already bound to a protein in solution, prior to lipid binding. The formation of ionic bridges is seen in the protein–lipid interaction between both protein C2 type domains and annexins..

Protein–lipid electrostatic interactions
Any positively charged protein will be attracted to a negatively charged membrane by nonspecific electrostatic interactions. However, not all peripheral peptides and proteins are cationic, and only certain sides of membrane are negatively charged. These include the cytoplasmic side of plasma membranes, the outer leaflet of bacterial outer membranes and mitochondrial membranes. Therefore, electrostatic interactions play an important role in membrane targeting of electron carriers such as cytochrome c, cationic toxins such as charybdotoxin, and specific membrane-targeting domains such as some PH domains, C1 domains, and C2 domains.

Electrostatic interactions are strongly dependent on the ionic strength of the solution. These interactions are relatively weak at the physiological ionic strength (0.14M NaCl): ~3 to 4 kcal/mol for small cationic proteins, such as cytochrome c, charybdotoxin or hisactophilin.

Spatial position in membrane
Orientations and penetration depths of many amphitropic proteins and peptides in membranes are studied using site-directed spin labeling, chemical labeling, measurement of membrane binding affinities of protein mutants, fluorescence spectroscopy, solution or solid-state NMR spectroscopy, ATR FTIR spectroscopy, X-ray or neutron diffraction, and computational methods.

Two distinct membrane-association modes of proteins have been identified. Typical water-soluble proteins have no exposed nonpolar residues or any other hydrophobic anchors. Therefore, they remain completely in aqueous solution and do not penetrate into the lipid bilayer, which would be energetically costly. Such proteins interact with bilayers only electrostatically, for example, ribonuclease and poly-lysine interact with membranes in this mode. However, typical amphitropic proteins have various hydrophobic anchors that penetrate the interfacial region and reach the hydrocarbon interior of the membrane. Such proteins "deform" the lipid bilayer, decreasing the temperature of lipid fluid-gel transition. The binding is usually a strongly exothermic reaction. Association of amphiphilic α-helices with membranes occurs similarly. Intrinsically unstructured or unfolded peptides with nonpolar residues or lipid anchors can also penetrate the interfacial region of the membrane and reach the hydrocarbon core, especially when such peptides are cationic and interact with negatively charged membranes.

Enzymes
Peripheral enzymes participate in metabolism of different membrane components, such as lipids (phospholipases and cholesterol oxidases), cell wall oligosaccharides (glycosyltransferase and transglycosidases), or proteins (signal peptidase and palmitoyl protein thioesterases). Lipases can also digest lipids that form micelles or nonpolar droplets in water.

Membrane-targeting domains (“lipid clamps")
Membrane-targeting domains associate specifically with head groups of their lipid ligands embedded into the membrane. These lipid ligands are present in different concentrations in distinct types of biological membranes (for example, PtdIns3P can be found mostly in membranes of early endosomes, PtdIns(3,5)P2 in late endosomes, and PtdIns4P in the Golgi). Hence, each domain is targeted to a specific membrane.
 * C1 domains and phorbol esters.
 * C2 domains bind phosphatidylserine, phosphatidylcholine or PtdIns(3,4)P2 or PtdIns(4,5)P2.
 * Pleckstrin homology domains, PX domains, and Tubby domains bind different phosphoinositides
 * FYVE domains are more specific for PtdIns3P.
 * ENTH domains bind PtdIns(3,4)P2 or PtdIns(4,5)P2.
 * ANTH domain binds PtdIns(4,5)P2.
 * Proteins from ERM (ezrin/radixin/moesin) family bind PtdIns(4,5)P2.
 * Other phosphoinositide-binding proteins include phosphotyrosine-binding domain and certain PDZ domains. They bind PtdIns(4,5)P2.
 * Discoidin domains of blood coagulation factors
 * ENTH, VHS and ANTH domains

Structural domains
Structural domains mediate attachment of other proteins to membranes. Their binding to membranes can be mediated by calcium ions (Ca2+) that form bridges between the acidic protein residues and phosphate groups of lipids, as in annexins or GLA domains.

Transporters of small hydrophobic molecules
These peripheral proteins function as carriers of non-polar compounds between different types of cell membranes or between membranes and cytosolic protein complexes. The transported substances are phosphatidylinositol, tocopherol, gangliosides, glycolipids, sterol derivatives, retinol, fatty acids, water, macromolecules, red blood cells, phospholipids, and nucleotides.
 * Glycolipid transfer proteins
 * Lipocalins including retinol binding proteins and fatty acid-binding proteins
 * Polyisoprenoid-binding protein, such as YceI protein domain
 * Ganglioside GM2 activator proteins
 * CRAL-TRIO domain (α-Tocopherol and phosphatidylinositol sec14p transfer proteins)
 * Sterol carrier proteins
 * Phosphatidylinositol transfer proteins and STAR domains
 * Oxysterol-binding protein

Electron carriers
These proteins are involved in electron transport chains. They include cytochrome c, cupredoxins, high potential iron protein, adrenodoxin reductase, some flavoproteins, and others.

Polypeptide hormones, toxins, and antimicrobial peptides
Many hormones, toxins, inhibitors, or antimicrobial peptides interact specifically with transmembrane protein complexes. They can also accumulate at the lipid bilayer surface, prior to binding their protein targets. Such polypeptide ligands are often positively charged and interact electrostatically with anionic membranes.

Some water-soluble proteins and peptides can also form transmembrane channels. They usually undergo oligomerization, significant conformational changes, and associate with membranes irreversibly. 3D structure of one such transmembrane channel, α-hemolysin, has been determined. In other cases, the experimental structure represents a water-soluble conformation that interacts with the lipid bilayer peripherally, although some of the channel-forming peptides are rather hydrophobic and therefore were studied by NMR spectroscopy in organic solvents or in the presence of micelles.

title: Peripheral membrane protein


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Talk:Archimedes

Crown or wreath?
Re this edit: There are not many versions of the story that refer to "Archimedes and the golden wreath"; I've never come across this before. This is because Vitruvius uses the word corona, which is usually translated into English as crown. As Chris Rorres points out, other historical research suggests that the crown would likely have been in the shape of a wreath.. Since Vitruvius does not give the exact shape of the crown, there is some WP:OR in assuming that it would have been a wreath, so it is safer not to put it into his voice.  ♦Ian Ma c M♦  (talk to me) 11:08, 25 June 2023 (UTC)

 * In the French cartoon Once Upon a Time... The Discoverers, the crown is shown as having a crown like shape. But we don't know, and this may be historically inaccurate.-- ♦Ian Ma c M♦  (talk to me) 11:28, 25 June 2023 (UTC)

 * The etymology of the word "crown", Latin corona, is indeed complex (see here ). Our image of a crown (e.g., The Crown) likely descends from the ancient diadem, not the wreath. Diadems began to replace wreaths as symbols of power and victory towards the end of Late Antiquity, as the ancient games, where wreaths were used, were no longer held sometime in the 5th century AD (see here and here for some examples). Vitruvius, however, lived in the 1st century BC, and for his readers a corona meant in all likelihood a wreath. In any case, this is too intricate for a regular reader to know, and your solution (i.e. mentioning the crown was likely a votive wreath) is sensible enough and should suffice for now. Thanks. -- Guillermind81 (talk) 16:01, 25 June 2023 (UTC)

Indiana Jones and the Dial of Destiny
In the new Indiana Jones film Indiana Jones and the Dial of Destiny, Jones goes on a search for the Archimedes Dial, a device capable of time travel. It is based on the Antikythera mechanism. This hasn't been added to the article yet, because the film is not released until 30 June in the USA. It probably will get added, but it runs into problems with WP:POPCULTURE, because it is not directly related to Archimedes other than the name, and there is no evidence that Archimedes designed the Antikythera mechanism.  ♦Ian Ma c M♦  (talk to me) 09:09, 28 June 2023 (UTC)

 * I agree with your assessment, as there was never an "Archimedes dial" and certainly not one that can travel through time. We do not know who built the Antikythera mechanism either but the evidence collected suggest it was likely not Archimedes. I know the temptation that adding such cultural references could bring more traffic to the article but I think popular cultural references that are so incidental to the person of Archimedes (such as that of the latest Indiana Jones movie) are better housed elsewhere. -- Guillermind81 (talk) 02:56, 6 July 2023 (UTC)

 * The release of the film worked wonders for the page views of this article, up from an average of around 2,500 a day to over 30,000 on 2 July. It's probably the first time that Archimedes has been a character in a big budget Hollywood movie, and he is played by Nasser Memarzia. The key WP:POPCULTURE requirement is sourcing showing why something is notable, and the film has very little to do with the actual work of Archimedes.-- ♦Ian Ma c M♦  (talk to me) 07:14, 6 July 2023 (UTC)

Remove metal bar demonstration (not relevant and explanation is wrong)
The section Archimedes' principle (anectode about volume of gold crown and bath; permalink) includes a demonstration. I am proposing to remove this demonstration because it is not related to the corresponding text, and because the explanation in the caption is incorrect:

 * The demonstration is related to Archimedes' principle (separate article), but it's not related to the anecdote in question (which is only about using displacement to measure volume). The idea that "the submerged crown would displace an amount of water equal to its own volume" is so simple that I don't think it requires any demonstration, and the current demonstration only creates confusion because it is counterintuitive and not related to the text.

-- Hddqsb (talk) 16:54, 14 September 2023 (UTC)
 * The caption says "A metal bar, placed into a container of water on a scale, displaces as much water as its own volume, increasing the mass of the container's contents and weighing down the scale." This is is incorrect. To see why, suppose the metal bar was replaced by an object of the same shape but with near-zero density. The container would still lower, even though no mass is "added" (whatever that means). The correct explanation is buoyancy: the water exerts an upward force on the object proportional to the displaced volume, and by Newton's Third Law the object exerts an equal and opposite force on the water, pushing the container down. The description of the file explains this correctly.

 * The story told by Vitruvius says only that Archimedes noticed that the water level of the bath rose as he got in, which is displacement of a fluid, and could be used to measure the volume of the crown. The video isn't what Vitruvius said so it is not a direct illustration. I also think that the video could be removed without a great loss. The illustration of the screw in the water is what Vitruvius actually says.-- ♦Ian Ma c M♦  (talk to me) 18:31, 14 September 2023 (UTC)
 * That illustration is perfect, thanks for finding it! (I did look earlier but couldn't find anything.) I'll go ahead and replace the video with this illustration in a couple of days if there are no objections. -- Hddqsb (talk) 08:03, 16 September 2023 (UTC)
 * I've gone ahead and swapped the video for the new image. Displacement-measurement.svg was uploaded to Wikimedia Commons in April 2022 so it is a relatively new image there. It does fit in with the text of the Vitruvius anecdote a lot better than the video.-- ♦Ian Ma c M♦  (talk to me) 09:51, 16 September 2023 (UTC)
 * Thanks! -- Hddqsb (talk) 15:54, 17 September 2023 (UTC)

Arcamidus was born in siracuse Sicily was not greek
arcamidus was born in siracuse Sicily was Sicilian 51.155.64.194 (talk) 09:05, 15 May 2024 (UTC)

FA Criteria
This article is deeply below FA standards, and unless immense and extensive improvements are made, it should go to WP:FAR. This may all sound harsh, but that's because the issues are so woven into the article's structure that most, if not all, sections would need to be completely rewritten to meet FA standards. I understand that various editors have attempted to maintain this page over the yeas, but its existing structure from the 2007 nomination has deeply limited such efforts.

There is poor sourcing all throughout; aside from non-existent citation formatting and sporadic page numbers, random web sources of highly variable notability are consistently prioritized over academic scholarship. In fact, I can't see that a single contemporary book-length survey of Archimedes is even touched, let a lone used extensively—why are they all in the further reading!

There are way too many references in the lead (see WP:LEADCITE), which seems to imply that the lead and the body are not matched at all. The lead includes no biographical information, and its structure is very difficult to follow.

The Biography section pulls directly and extensively from ancient sources, without any filtering through modern commentary. Citations are sporadic and inconsistent. The discoveries and mathematics sections are extremely choppy and brief. Every single work of his does not need its own subsection just to include two (usually uncited) sentences. The legacy section is merely a list of length quotes and random trivia; no information on his actual influence into later mathematics is explained.

There is much more to say, but in conclusion I'm afraid the issues are rather extreme.  Aza24  (talk)   20:20, 27 June 2024 (UTC)

 * We don't know much about the life of Archimedes and everything we do know was written long after his death; the article makes this clear. I'm not sure how "filtering through modern commentary" would help, as he has been dead for over two thousand years. This is a weird argument to make.-- ♦Ian Ma c M♦  (talk to me) 08:03, 28 June 2024 (UTC)
 * Hi there, this is a rather revealing point to harp on, and I highly recommend you take a look at some recent FAs (Leucippus, for instance) and read WP:Primary. Every featured article needs to be "a thorough and representative survey of the relevant literature; claims are verifiable against high-quality reliable sources and are supported by inline citations where appropriate". Primary sources are simply not allowed in place of suitable secondary ones. You can disagree with this all you like, but you will find that no reviewers will agree. The aforementioned Leucippus, for example, has a biography section only citing academic articles and books from the last 20 years (albeit a single one from 1979).
 * Yes, "he has been dead for over two thousand years"—exactly! So scholars have had two thousand years to analyze, update and revise his biography! Would you really claim that there are no scholars which have altered, changed, updated, reinterpreted his biography from 2000 year old accounts?
 * I understand it is easy to see my comments as "[weird] argument[s]", but this is a misunderstanding. I am citing real and rather egregious issues, after having review hundreds of articles for FAC & FAR, in content and source reviews. This article falls extremely flat, and defending it will take you no where, unfortunately.  Aza24  (talk)   18:07, 28 June 2024 (UTC)

 * Sorry, this is still a weird argument. We know very little about the life of Archimedes other than what was said by Roman historians many years after his death. I'm not sure what these "modern sources" are supposed to be, perhaps you could find them if it is such a problem. I don't have access to specialist academic libraries or paywalled academic resources, so it is hard for me to know exactly what you want here. We know that many of the things said by the Roman historians are likely to be apocryphal, which is why they are treated with caution.-- ♦Ian Ma c M♦  (talk to me) 18:28, 28 June 2024 (UTC)
 * "which is why they are treated with caution" — they shouldn't be treated at all... that's WP:Original Research, please read WP:Primary, we do not interpret primary sources on Wikipedia. This is a tertiary encyclopedia that summarizes secondary sources. We don't cite from Roman sources directly, period, and we definitely do not in featured articles.
 * Where are the modern sources? How about the huge Further reading section that includes multiple major recent surveys? Why is not a single one of them included? How can this be "a thorough and representative survey of the relevant literature; claims are verifiable against high-quality reliable sources and are supported by inline citations where appropriate"?  Aza24  (talk)   18:44, 28 June 2024 (UTC)
 * A lot of the sourcing in Leucippus seems to be from specialist academic sources. I don't have easy access to this type of material and people who want to read the sources for themselves would also have this problem. However, I accept your point on this.-- ♦Ian Ma c  M♦  (talk to me) 18:57, 28 June 2024 (UTC)
 * I appreciate that. Certainly that material is more difficult to access, but nowadays there are more resources for that. GoogleBooks includes extensive previews, and Archive.org is a goldmine for academic sources. You'll see that the further reading section already includes quite a few links to archive.org copies, which are freely available to borrow (sometimes a free registration is needed).  Aza24  (talk)   19:17, 28 June 2024 (UTC)
 * @Aza24, @Ianmacm. Sounds like a heated discussion is occurring. I pinged both WP:WPM and WP:PHY for more opinions. Dedhert.Jr (talk) 02:30, 29 June 2024 (UTC)
 * It would help if someone dug up recent scholarly work that evaluated the traditional tales and checked them for consistency, plausibility, etc. Something like what the Stanford Encyclopedia of Philosophy does for Pythagoras. I don't see a fundamental problem with our reporting "Cicero said..." as long as we have further, modern sources to contextualize that. Nothing in the WP:NOR policy forbids judicious use of primary sources. (Indeed, I'd actually fault the Leucippus article for not giving direct pointers to editions/translations of the ancient sources; that's mildly inconvenient! When we say, for example, Plato explored cosmological ideas similar to those of Leucippus in the dialogue Timaeus, a reader shouldn't have to get a paywalled journal article to find which sections of the Timaeus are relevant.) XOR'easter (talk) 04:54, 29 June 2024 (UTC)
 * Leucippus doesn't even try to link to the source texts where its claims originate. This does a disservice to readers, because it makes them jump through hoops to figure out what was actually said. I imagine in most if not all cases there are online scans of these texts and probably also translations. Frankly I am not impressed. All of the content is along the lines of "So-and-so says Leucippus says XYZ" where so-and-so was writing a few centuries after Leucippus, but then the link shows that Wikipedia's text is a paraphrase of some paywalled academic paper where the author paraphrased an earlier Greek/Roman source who was paraphrasing Leucippus, so what Wikipedia readers are getting is 4 steps removed from the original. This helps tick off FA boxes, and might help scholars looking for a list of recent works to cite, but readers would probably be better off with a direct quotation of the oldest extant work or a translation. –jacobolus (t) 04:54, 29 June 2024 (UTC)
 * The sourcing in Leucippus has a high gloss sheen, but if someone wanted to actually read and verify the cites it would be very difficult. I have tried to stick to easy to follow cites, not what someone said about it on page 336 of an obscure or paywalled academic work.-- ♦Ian Ma c M♦  (talk to me) 06:43, 29 June 2024 (UTC)

I agree overall with jacobolus and Ian, and appreciate the "high gloss sheen" comment in particular. I think there is no problem citing ancient sources appropriately in the biographical sections. While I haven't looked that closely, everything I looked at sourced to an ancient source also had a secondary source nearby. E.g., Something about ancient source [ footnote to ancient source ]. Another sentence or two.[ footnote to secondary source ]

There are some sourcing issues to be sure (which are very easy to fix!) The mathematics section needs better sources, as there are some paragraphs lacking footnotes. But this material is so standard as to be found in tertiary sources like Kline, or Boyer and Merzbach. Perhaps the sections in Archimedes works each should be individually referenced with a footnote to the Heath source (which provides commentary, and therefore is a secondary source on the works of Archimedes), as this remains the standard modern reference for Archimedes works. Only the palimpsest, which post-dates Heath, needs to be referenced separately (which it is). In any case, concerns over the lack of sourcing of this section are overwrought, considering the extremely high quality references Knorr and Sato that are very explicitly intended to support the section as a whole.

The "Legacy" section is also very weak. It's hard to overstate the continuing legacy of Archimedes in mathematics: one could go so far as to say that he invented mathematics as we know it. The section doesn't even try. Tito Omburo (talk) 11:46, 29 June 2024 (UTC)

 * Primary sources are not the main problem here. It is the lack of academic secondary sources (which extends to the entire article). The FA criteria are explicit in asking for "a thorough and representative survey of the relevant literature". Outside of the lead, there is a single book on Archimedes sourced. The result is highly noticeable in the article, as you point out, the mathematics sections and legacy are surprisingly sparse, and the reliance on solely primary sources (or not sources) for large swathes of text is not ideal.
 * These academic sources are not niche or hard-to-acess. Archimedes lists multiple works by clearly established historians, and includes direct links to archive.org which is freely available. If one wants to actually engage in a "thorough and representative survey of the relevant literature", this will include academic sources which are sometimes difficult to access. That's why Wikipedia exists, to make such information more accessible.
 * If I only used web/non-academic sources when I wrote the now-FA Cai Lun, it would have been a paragraph long, maybe two. You'll see that I linked almost every page number to google books: readers can click on any one and immediately find the information. How is this difficult to access? By the way, I regularly used plenty of primary sources in Cai Lun and found no issues at FAC; this is because I paired each one with a secondary source, which is certainly more advisable (and productive) than sole reliance on primary sources.
 * In any case, there seems to be some confusion. I'm not saying this is a bad article, or even that the sourcing is bad, I'm saying that it does not match the Featured article criteria. Alas, these are two very different things, and you are all welcome to (rather bizarrely) dig on Leucippus all you want, but it reflects the reality of what FAs are now a-days.  Aza24  (talk)   18:18, 29 June 2024 (UTC)
 * Where is there reliance exclusively on primary sources? Tag some specific problems, please.  A side note is that many of the sources listed in further reading are very pulpy.  E.g., Netz and Noel is not a scholarly or academic source, and some of the others are, rather more obviously, probably not good references.  Boyer is a tertiary source, generally good (I suggested above for the mathematics section), but there are better secondary sources.  Clagett is a very good source, but also specifically focuses on mathematics in the middle ages, and is incredibly detailed: we already cite his survey article on this topic.  I think the Dijksterhuis is a good source, particularly for the life of Archimedes, that could be used for some of the history section, and also for the mathematics section.  Tito Omburo (talk) 18:45, 29 June 2024 (UTC)
 * Almost the entire biography is exclusively relying on primary sources; please note that these "Rorres, Chris" citations are just a web page with a public domain translation of Greek authors.
 * The biography's first paragraph does not have primary sources; it includes a source from 1897 (?), a 1975 journal article and a dictionary entry, the latter two being some of the only scholarship in the whole section. The last sentence is uncited.
 * The biography's second paragraph is only primary sources
 * The biography's third paragraph is only primary sources (save for the line "He also mentions that Marcellus brought to Rome two planetariums Archimedes built")
 * The biography's fourth paragraph is only primary sources, save for the its last line (I checked the Jaeger source and it only covers the last line).
 * The biography's final paragraph is only primary sources
 * Now this is just a single section, I suspect there are plenty of others. Other examples (from a glance) include the first paragraph of the Heat ray section and the second paragraph of the Astronomical instruments. –  Aza24  (talk)   18:59, 29 June 2024 (UTC)
 * Sorry, I'm not trying to rag on Leucippus, which is certainly above average for Wikipedia articles; it was just your example of exceptional citation formatting, but I don't really like the style with a plethora of footnotes often crammed together but none of them giving any detail or quotations, and in my opinion the primary sources are essential to cite in this kind of article, but there are missing. Your focus on sources from the past decade or two also seems misplaced. To my knowledge Archimedes isn't a subject of such rapid historiographical change that commentary from 50, 100, or 1000 years ago is necessarily obsolete.
 * In any event, it's a somewhat apples-to-oranges comparison because Archimedes is a dramatically more productive, known-about, and influential figure than Leucippus. I agree with you that this article is far from comprehensive, but on the other hand if it were expanded to the level of detail found in Leucippus or Cai Lun relative to the amount of available material about Archimedes, it would be probably 5x longer than currently – the mathematics section alone would be longer than the current article – and we'd have people complaining that GA/FAs need to be short enough to read in one sitting or whatever.
 * Anyway... Do you have some specific recommended recent literature that you think should be added here? One thing I'd like to see in particular is some discussion of Archimedes' influence on the mathematics and science of the medieval Islamic world, which is currently unmentioned. –jacobolus (t) 20:25, 29 June 2024 (UTC)
 * One source people may want to look at with some counterfactual speculation about Archimedes' influence is the recent issue of Interdisciplinary Science Reviews (Volume 47 Issue 3-4, 2022), edited by Chemla, which involved a paper by Netz, "The place of Archimedes in world history", accompanied by responses from 13 other scholars. Wikipedia editors with moderate experience can access these via The Wikipedia Library at https://journals-sagepub-com.wikipedialibrary.idm.oclc.org/toc/idsa/47/3-4 –jacobolus (t) 00:22, 30 June 2024 (UTC)
 * Another possibly useful source relevant to Archimedes' influence is the 2010 conference proceedings The Genius of Archimedes edited by Paipetis and Ceccarelli. –jacobolus (t) 02:25, 2 July 2024 (UTC)
 * Does anyone have the energy to find page numbers in Dijksterhuis, Heath, etc.? Citing these long books without more specifics seems a bit mean to readers. –jacobolus (t) 01:45, 30 June 2024 (UTC)
 * Here are my two cents: Netz has been publishing and translating Archimedes for over two decades, but almost everything worth reading from him is behind paywalls and he believes writing a "biography" of Archimedes is pointless. Knorr is better overall but his work is behind even more impenetrable paywalls. Heath is terribly outdated and should be used with caution, while Dijksterhuis is about the best your regular, "I don't work for academia" person could have access right now. Believer or not, Heiberg's work still holds on and its packed with lots of good textual and biographical information but you'll have to read German (and Latin!) to make sense of it. Bottom line, the best sources are the most esoteric, hard to reach ones, while the popular sources are often worth crap.
 * I do agree the article needs a major Enterprise "refit" to keep it FA worthy, just wanted you to know what we might be up against.
 * -- Guillermind81 (talk) 04:43, 2 July 2024 (UTC)
 * Dijksterhuis (which I only skimmed parts of) seems like an excellent source, and the consensus seems to be that it is the best available biography. I think we should pull it out in a new section of "Works Cited" or whatever, and then liberally add footnotes citing specific chapters and pages for every currently unsourced section of this article. It's kind of a lot of grunt work, but especially if we include links to a scan (the IA scan is unfortunately "borrow unavailable, presumably by request of Princeton Univ. Press) should be at least moderately helpful to readers, and might satisfy some of the footnote police. –jacobolus (t) 05:29, 2 July 2024 (UTC)

Heat ray section
Quick aside [from the FA criteria discussion above], @Guillermind81 semi-reverted my direct quotation of Lucian "Archimedes 'burned the enemy ships by means of his skill' " and replaced it with just "Archimedes burned enemy ships", in. Personally I think the direct quotation is helpful here, since the unquoted version makes it sound like we're paraphrasing a comment talking about focusing reflectors per se, whereas the direct quotation makes it clear that Lucian didn't include any specifics other than crediting "skill" (techne) [it might even be worth quoting as "burned the enemy ships by means of his techne" or "burned the enemy ships by means of his skill"]. I understand that we're trying to keep this brief here and offload details to the (currently mediocre and incomplete) Archimedes' heat ray, but we also want to try to give readers the least misleading brief summary we can. What do other folks think? –jacobolus (t) 05:17, 2 July 2024 (UTC)
 * The reason why it may read like that is the preceding sentence about Diocles that was not originally there. I'm all for taking Diocles out, rather than add even more stuff to this, as I keep arguing the discussion better belongs to the Archimedes heat ray entry. Maybe our efforts should divert there if said article is not up to par.
 * -- Guillermind81 (talk) 05:38, 2 July 2024 (UTC)
 * I do appreciate your effort to keep this brief. Perhaps someone else has an idea how to make a few sentence summary that conveys that there's no contemporaneous evidence about the "heat ray" and 2nd century mentions point to some kind of incendiary (perhaps some precursor to Greek fire or the like) but by ~600 AD there was apparently an established legend about reflectors and ships. –jacobolus (t) 05:46, 2 July 2024 (UTC)
 * Africa 1975 says: «In the Hellenistic age, scientists such as Apollonius and Diocles were interested in the theoretical aspects of burning mirrors and may have experimented with them,10 but there is no reference to the practical application of a heat ray in warfare until the second half of the second century A.D. when Lucian mentions in passing that Archimedes burned ships "with his skill" (Hippias 2). Lucian did not identify the weapon, and Galen is the first author to specify mirrors as the source of heat. II Where he picked up the story is not known, but it was commonplace among scholars of the time to attribute all manner of wonders to famed sages of the past. Galen's younger contemporary, Cassius Dio, was also aware of the mirrors, for Zonaras (9.4) mentions them in his epitome of Dio's Fifteenth Book.» But I am not sure if this is an entirely accurate summary. –jacobolus (t) 05:54, 2 July 2024 (UTC)
 * That's accurate as far as tracing the complicated history of a "scientific" fable goes, and yes most of the time it's a game of broken telephone. But why burden the reader with all of this? Scholars have to make a living after all, sure, but I fail to see how this information will serve the reader. Guillermind81 (talk) 06:04, 2 July 2024 (UTC)
 * The apocryphal story of the "heat ray" has clearly been of interest to readers, and it's worth being clear that it's a legend that is surely made up. I agree the details might be unnecessary here. I'd be fine with condensing the whole section down to a paragraph or so, delegating some details to a couple of footnotes and the rest to Archimedes' heat ray. I'm just not sure what that paragraph should say. Maybe we should be leading along the lines of, "As legend has it, Archimedes focused the light of the sun using large mirrors and set Roman ships ablaze at the siege of Syracuse..." –jacobolus (t) 06:09, 2 July 2024 (UTC)
 * I propose we leave the section as is for now and let others weigh in before editing any more. It's getting late and I don't want us to inadvertently start the next Great Edit War. Guillermind81 (talk) 06:15, 2 July 2024 (UTC)
 * I took another crack at it. Is that any better? –jacobolus (t) 10:27, 11 July 2024 (UTC)
 * Looks OK to me (one of the links was dead but salvageable). XOR'easter (talk) 17:30, 12 July 2024 (UTC)

title: Talk:Archimedes


text:
Seleucus V Philometor

The Seleucid king Seleucus V Philometor (Greek: Σέλευκος Ε΄ ὁ Φιλομήτωρ; 126/125 BC), ruler of the Hellenistic Seleucid kingdom, was the eldest son of Demetrius II Nicator and Cleopatra Thea. The epithet Philometor means "mother-loving" and in the Hellenistic world usually indicated that the mother acted as co-regent for the prince.

Biography
Just before Antiochus VII Sidetes died fighting the Parthian Empire in late 129, the Parthian king Phraates II had released Demetrius II, who entered Syria in ca. September 129. This forced Seleucus V's half-brother Antiochus IX to flee to Cyzicus. Cleopatra Thea remarried Demetrius and reunited him with his two sons, Seleucus V and Antiochus VIII.

The Parthians captured Antiochus VII's son, also named Seleucus, and Laodice, Seleucus V's sister, who had accompanied the fallen king on campaign. Phraates married Laodice, and showed great favor to Seleucus, son of Antiochus VII. While Demetrius II was preoccupied fighting the usurper Alexander II Zabinas, the Parthians sent this Seleucus back to Syria, hoping he could take the throne as their puppet king. The attempt failed, and he spent the rest of his life in Parthia.

Instead, after his father was murdered outside of Tyre in 125, Seleucus V claimed the throne as the eldest son of Demetrius II; however, he was soon killed by his own mother. According to Appian, Cleopatra Thea had aided in the death of Demetrius and feared that Seleucus V might avenge his father. This encouraged her to remove Seleucus in favor of his younger brother, Antiochus VIII.

title: Seleucus V Philometor


text:
Talk:Belinda Laracuente

Untitled
What is a quiropractor? Is it a badly spelt chiropractor? (Maybe this is the spanish for chiropractor?) -- SGBailey 21:45 Jan 12, 2003 (UTC)

title: Talk:Belinda Laracuente


text:
Folk rock

Folk rock is a fusion genre of rock music with heavy influences from pop, English and American folk music. It typically combines elements of folk and rock music together, it arose in the United States, Canada, and the United Kingdom in the mid-1960s. In the U.S., folk rock emerged from the folk music revival. Performers such as Bob Dylan and the Byrds—several of whose members had earlier played in folk ensembles—attempted to blend the sounds of rock with their pre-existing folk repertoire, adopting the use of electric instrumentation and drums in a way previously discouraged in the U.S. folk community. The term "folk rock" was initially used in the U.S. music press in June 1965 to describe the Byrds' music.

The commercial success of the Byrds' cover version of Dylan's "Mr. Tambourine Man" and their debut album of the same name, along with Dylan's own recordings with rock instrumentation—on the albums Bringing It All Back Home (1965), Highway 61 Revisited (1965), and Blonde on Blonde (1966)—encouraged other folk acts, such as Simon & Garfunkel, to use electric backing on their records and new groups, such as Buffalo Springfield, to form. Dylan's controversial appearance at the Newport Folk Festival on 25 July 1965, where he was backed by an electric band, was also a pivotal moment in the development of the genre.

During the late 1960s in Britain and Europe, a distinct, eclectic British folk rock style was created by Pentangle, Fairport Convention and Alan Stivell. Inspired by British psychedelic folk and the North American style of folk rock, British folk rock bands began to incorporate elements of traditional British folk music into their repertoire, leading to other variants, including the overtly English folk rock of the Albion Band and Celtic rock.

Definition and etymology
"Folk rock" refers to the blending of elements of folk and rock music, which arose in the U.S. and UK in the mid-1960s. The genre was pioneered by the Byrds, who began playing traditional folk music and songs by Bob Dylan with rock instrumentation, in a style heavily influenced by the Beatles and other British Invasion bands. The term folk rock was coined in the June12, 1965, issue of the American music magazine Billboard by the journalist Eliot Siegel. Siegel used the term principally to describe the music of the Byrds, who had issued their debut album in the U.S. that month. In the same article, he wrote that Billy J. Kramer, Jackie DeShannon and Sonny & Cher had all started incorporating "folk-oriented material on singles", and he listed Rising Sons, Joe and Eddie and the Lovin' Spoonful as new folk-rock acts. Dylan also contributed to the creation of the genre, with his recordings utilizing rock instrumentation on the albums Bringing It All Back Home, Highway 61 Revisited, and Blonde on Blonde.

In a broader sense, folk rock encompasses similarly inspired musical genres and movements in different regions of the world. Folk rock may lean more towards either folk or rock in instrumentation, playing and vocal style, and choice of material. While the original genre draws on music of Europe and North America, there is no clear delineation of which other culture's music might be included as influences.

Folk revival

The American folk-music revival began during the 1940s; building on the interest in protest folk singers such as Woody Guthrie and Pete Seeger, it reached a peak in popularity in the mid-1960s with artists such as Bob Dylan and Joan Baez. In 1948, Seeger formed the Weavers, whose mainstream popularity set the stage for the folk revival of the 1950s and early 1960s and also served to bridge the gap between folk, popular music, and topical song. The Weavers' sound and repertoire of traditional folk material and topical songs directly inspired the Kingston Trio, a three-piece folk group who came to prominence in 1958 with their hit recording of "Tom Dooley". The Kingston Trio provided the template for a flood of "collegiate folk" groups between 1958 and 1962.

At roughly the same time as these "collegiate folk" vocal groups came to national prominence, a second group of urban folk revivalists, influenced by the music and guitar picking styles of folk and blues artist such as Woody Guthrie, Lead Belly, Brownie McGhee, and Josh White, also came to the fore. Many of these urban revivalists were influenced by recordings of traditional American music from the 1920s and 1930s, which had been reissued by Folkways Records; Harry Smith's Anthology of American Folk Music was particularly influential. While this urban folk revival flourished in many cities, New York City, with its burgeoning Greenwich Village coffeehouse scene and population of topical folk singers, was widely regarded as the centre of the movement. Out of this fertile environment came such folk-protest luminaries as Bob Dylan, Tom Paxton, Phil Ochs, and Peter, Paul and Mary, many of whom would transition into folk rock performers as the 1960s progressed.

The vast majority of the urban folk revivalists shared a disdain for the values of mainstream American mass culture and led many folk singers to begin composing their own "protest" material. The influence of this folk-protest movement would later manifest itself in the sociopolitical lyrics and mildly anti-establishment sentiments of many folk rock songs, including hit singles such as "Eve of Destruction", "Like a Rolling Stone", "For What It's Worth", and "Let's Live for Today".

During the 1950s and early 1960s in the UK, a parallel folk revival referred to as the second British folk revival, was led by folk singers Ewan MacColl and Bert Lloyd. Both viewed British folk music as a vehicle for leftist political concepts and an antidote to the American-dominated popular music of the time. However, it was not until 1956 and the advent of the skiffle craze that the British folk revival crossed over into the mainstream and connected with British youth culture. Skiffle renewed popularity of folk music forms in Britain and led directly to the progressive folk movement and the attendant British folk club scene. Among the leading lights of the progressive folk movement were Bert Jansch and John Renbourn, who would later form the folk rock band Pentangle in the late 1960s. Other notable folk rock artists with roots in the progressive folk scene were Donovan, Al Stewart, John Martyn and Paul Simon.

The Beatles and the British Invasion
Beginning in 1964 and lasting until roughly 1966, a wave of British beat groups, including the Beatles, the Rolling Stones, the Dave Clark Five, Gerry & the Pacemakers, the Kinks, and Herman's Hermits amongst others, dominated the U.S. music charts. These groups were all heavily influenced by American rock 'n' roll, blues, and R&B—musical genres they had been introduced to via homegrown British rock 'n' roll singers, imported American records, and the music of the skiffle craze. These UK groups, known collectively as the British Invasion, reintroduced American youth culture to the broad potential of rock and pop music as a creative medium and to the wealth of musical culture to be found within the United States.

Of particular importance to the development of folk rock by the British Invasion were the subtle folk influences evident in such Beatles' compositions as "I'll Be Back", "Things We Said Today", and "I'm a Loser", with the latter song being directly inspired by folk singer-songwriter Bob Dylan. In the opinion of Roger McGuinn of the Byrds, writers who attempt to define the origins of folk rock "don't realise that the Beatles were responsible as far back as 1963". He cites "She Loves You" as one of the first examples where the Beatles introduced folk chord changes into rock music and so initiated the new genre. These songs were all influential in providing a template for successfully assimilating folk-based chord progressions and melodies into pop music. This melding of folk and rock 'n' roll in the Beatles' music became even more explicit during 1965, with the release of "You've Got to Hide Your Love Away", a folk-derived song with introspective lyrics, again influenced by Dylan. Although the Beatles themselves utilized folk as just one of many styles evident in their music, the underlying folk influences in a number of their songs would prove to be important to folk rock musicians attempting to blend their own folk influences with beat music.

The effect that the music of these British bands, and the Beatles in particular, had on young Americans was immediate; almost overnight, folk—along with many other forms of homegrown music—became passé for a large proportion of America's youth, who instead turned their attention to the influx of British acts. The influence of these acts also impacted on the collegiate folk and urban folk communities, with many young musicians quickly losing interest in folk music and instead embracing the rock 'n' roll derived repertoire of the British Invasion. Future members of many folk rock acts, including the Byrds, Jefferson Airplane, the Lovin' Spoonful, the Mamas & the Papas, and Buffalo Springfield, all turned their backs on traditional folk music during 1964 and 1965 as a direct result of the influence of the Beatles and the other British Invasion bands. Author and music historian Richie Unterberger has noted that the Beatles' impact on American popular culture effectively sounded the death knell for the American folk music revival.

In addition to The Beatles, the two British groups that were arguably the most influential on the development of folk rock were the Animals and the Searchers. The Animals released a rock interpretation of the traditional folk song "The House of the Rising Sun" in the U.S. in August 1964. The song reached number 1 on the Billboard Hot 100 singles chart and stayed there for three weeks, selling over a million copies in just five weeks in the U.S. The band's arrangement of "The House of the Rising Sun", which transmuted the song from an acoustic folk lament to a full-bore electric rock song, would go on to influence many folk rock acts but none more so than Dylan himself, who cited it as a key factor in his decision to record and perform with an electric rock band in 1965.

Electric Twelve-String Guitar in Folk Music
The Searchers were influential in popularizing the jangly sound of the electric twelve-string guitar. Many musicians in the collegiate and urban folk movements were already familiar with acoustic twelve-string guitars via the music of folk and blues singer Lead Belly. However, the Searchers' use of amplified twelve-strings provided another example of how conventional folk elements could be incorporated into rock music to produce new and exciting sounds. The Beatles' lead guitarist, George Harrison, also influenced this trend towards jangly guitars in folk rock with his use of a Rickenbacker twelve-string guitar on the Beatles' mid-1960s recordings. This relatively clean, jangly sound—without distortion or other guitar effects—became a cornerstone of folk rock instrumentation and was used in many American folk rock records made during 1965 and 1966.

Other precursors
Although folk rock mainly grew out of a mix of American folk revival and British Invasion influences, there were also a few examples of proto-folk rock that were important in the development of the genre. Of these secondary influences, Unterberger has cited the self-penned, folk-influenced material of San Francisco's the Beau Brummels as arguably the most important. Despite their Beatlesque image, the band's use of minor chords, haunting harmonies, and folky acoustic guitar playing—as heard on their debut single "Laugh, Laugh"—was stylistically very similar to the later folk rock of the Byrds. Released in December 1964, "Laugh, Laugh" peaked at number 15 on the Billboard Hot 100 in early 1965, while its similarly folk-flavored follow-up, "Just a Little", did even better, reaching number 8 on the U.S. singles chart. The high-profile success of the Beau Brummels' music was important in demonstrating that a hybrid of folk and rock could potentially be translated into mainstream commercial success.

Pre-dating the Beau Brummels' commercial breakthrough by almost two years, singer-songwriter Jackie DeShannon's April 1963 single "Needles and Pins" marked, according to Unterberger, the earliest appearance of the ringing guitar sound that would become a mainstay of early folk rock. This use of cyclical, chiming guitar riffs was repeated on DeShannon's late 1963 recording of her own composition "When You Walk in the Room". The following year, both songs would become hits for the Liverpudlian band the Searchers, who chose to place even greater emphasis on the jangly guitar playing in the songs. In addition, a number of DeShannon's songs from the period, including "When You Walk in the Room", displayed a greater degree of lyrical maturity and sensuality than was usual for pop songs of the time. This heightened degree of emotional introspection was inspired by her love of Bob Dylan's folk songwriting and represents one of the first attempts by an American artist to absorb folk sensibilities into rock music.

In the UK, the folk group the Springfields (featuring Dusty Springfield) had been releasing folk-oriented material featuring full band arrangements since the early 1960s, including renditions of "Lonesome Traveler", "Allentown Jail", and "Silver Threads and Golden Needles". Although these records owed more to orchestral pop than rock, they were nonetheless influential on up-and-coming folk rock musicians on both sides of the Atlantic. In mid-1965, folk singer-songwriter Donovan was also experimenting with adding electrified instrumentation to some of his folk and blues-styled material, as evidenced by songs such as "You're Gonna Need Somebody on Your Bond" and "Sunny Goodge Street". In spite of his folky persona and repertoire, Donovan himself had always considered himself a pop star, rather than a folk singer. As a result, he had been thinking of a way in which to introduce folk styled acoustic guitars and socially conscious lyrics into pop music for several years prior to his 1965 breakthrough as a recording artist. By January 1966, he had recorded the self-penned hit "Sunshine Superman" with a full electric backing band.

Other bands and solo artists who were blurring the boundaries between folk and rock in the early 1960s include Judy Henske, Richard and Mimi Fariña, and the Mugwumps, the latter of which were a New York band featuring future members of the Lovin' Spoonful and the Mamas & the Papas. Also of note are the Australian band the Seekers, who had relocated to England in 1964 and reached number 1 on the UK Singles Chart with "I'll Never Find Another You" in February 1965. Unterberger has noted that, although it was not strictly a folk song, "I'll Never Find Another You" was heavily influenced by Peter, Paul and Mary and featured a cyclical, twelve-string guitar part that sounded similar to the guitar style that Jim McGuinn of the Byrds would popularize later that same year.

There are also a few antecedents to folk rock present in pre-British Invasion American rock 'n' roll, including Elvis Presley's 1954 cover of the Bill Monroe bluegrass standard "Blue Moon of Kentucky"; Buddy Holly's self-penned material, which strongly influenced both Dylan and the Byrds; Ritchie Valens' recording of the Mexican folk song "La Bamba"; Lloyd Price's rock 'n' roll adaptation of the African-American folk song "Stagger Lee" (originally recorded by Mississippi John Hurt in 1928); Jimmie Rodgers' rock 'n' roll flavored renditions of traditional folk songs; and the folk and country-influenced recordings featured on the Everly Brothers' 1959 album Songs Our Daddy Taught Us.

The Byrds
The moment when all of the separate influences that served to make up folk rock finally coalesced into an identifiable whole was with the release of the Byrds' recording of Bob Dylan's "Mr. Tambourine Man". The term "folk rock" was coined by the U.S. music press to describe the band's sound in June 1965, at roughly the same time as "Mr. Tambourine Man" peaked at number 1 on the Billboard chart. Within three months it had become the first folk rock smash hit, reaching number 1 on both the Billboard Hot 100 and the UK Singles Chart. The single's success initiated the folk rock boom of 1965 and 1966, during which a profusion of Byrds-influenced acts flooded the American and British charts. In particular, the Byrds' influence can be discerned in mid-1960s recordings by acts such as the Lovin' Spoonful, Barry McGuire, the Mamas & the Papas, Simon & Garfunkel, Jefferson Airplane, the Turtles, We Five, Love, and Sonny & Cher.

It was during the rehearsals at World Pacific that the band began to develop the blend of folk music and Beatles-style pop that would characterize their sound. However, this hybrid was not deliberately created; it evolved organically out of some of the band members' own folk music roots and their desire to emulate the Beatles. The band's folk influences, lack of experience with rock music forms, and Beatleseque instrumentation all combined to color both their self-penned material and their folk derived repertoire. The band themselves soon realized that there was something unique about their music and, with Dickson's encouragement, they began to actively attempt to bridge the gap between folk and rock.

Mr. Tambourine Man's blend of abstract lyrics, folk-influenced melody, complex harmonies, jangly 12-string Rickenbacker guitar playing, and Beatles-influenced beat, resulted in a synthesis that effectively created the subgenre of folk rock. The song's lyrics alone took rock and pop songwriting to new heights; never before had such intellectual and literary lyrics been combined with rock instrumentation by a popular music group.

Dylan's material would provide much of the original grist for the folk rock mill, not only in the U.S. but in the UK as well, with many pop and rock acts covering his material in a style reminiscent of the Byrds. Their reworking of "Mr. Tambourine Man", along with the Animals' rock interpretation of "The House of the Rising Sun" (itself based on Dylan's earlier cover), helped to give Dylan the impetus to start recording with an electric backing band.

As the 1970s dawned, folk rock evolved away from the jangly template pioneered by the Byrds, but their influence could still be heard in the music of bands like Fairport Convention and Pentangle. The Byrds themselves continued to enjoy commercial success with their brand of folk rock throughout 1965, most notably with their number 1 single "Turn! Turn! Turn!". By the start of 1966, however, the group had begun to move away from folk rock and into the new musical frontier of psychedelic rock. The folk rock sound of the Byrds has continued to influence many bands over the years, including Big Star, Tom Petty and the Heartbreakers, R.E.M., the Long Ryders, the Smiths, the Bangles, the Stone Roses, and Teenage Fanclub, among others.

Bob Dylan
Five days before the Byrds entered Columbia Studios in Hollywood to record his song "Mr. Tambourine Man", Bob Dylan completed the recording sessions for his fifth album, Bringing It All Back Home. Of the eleven tracks on the album, seven featured Dylan backed by a full electric rock band, in stark contrast to his earlier acoustic folk albums. Dylan's decision to record with an electric backing band had been influenced by a number of factors, including the Beatles' coupling of folk derived chord progressions and beat music, the Byrds' rock adaptation of "Mr. Tambourine Man" (which Dylan had heard at a Byrds' rehearsal in late 1964), and the Animals hit cover of "The House of the Rising Sun".

Bringing It All Back Home was released on 22 March 1965, peaking at number 6 on the Billboard Top LPs chart and #1 on the UK Album Chart. The album's blend of rhythm and blues-derived rock and abstract, poetic lyrics was immediately influential in demonstrating that intelligent lyrical content could be wedded with rock 'n' roll. The songs on the album saw Dylan leaving folk music far behind. Even with this folkier, acoustic material, Dylan's biting, apocalyptical, and often humorous lyrics went far beyond those of contemporary folk music, particularly the folk-protest music with which he had been previously associated.

On 20 July 1965, Dylan released the groundbreaking "Like a Rolling Stone", a six-minute-long scathing put-down, directed at a down-and-out society girl, which again featured Dylan backed by an electric rock band. Released just as the Byrds' cover of "Mr. Tambourine Man" topped the charts in the United States, the song was instrumental in defining the burgeoning folk rock scene and in establishing Dylan as a bona fide rock star, rather than a folksinger. "Like a Rolling Stone" managed to reach the Top 5 on both sides of the Atlantic. Five days after the release of "Like a Rolling Stone", on 25 July 1965, Dylan made a controversial appearance at the Newport Folk Festival, performing three songs with a full band. He was met with derisive booing and jeering from the festival's purist folk music crowd, but in the years since the incident, Dylan's 1965 Newport Folk Festival appearance has become widely regarded as a pivotal moment in the synthesis of folk and rock.

Dylan followed "Like a Rolling Stone" with the wholly electric album Highway 61 Revisited and the non-album single "Positively 4th Street", which itself has been widely interpreted as a rebuke to the folk purists who had rejected his new electric music. Throughout 1965 and 1966, hit singles like "Subterranean Homesick Blues", "Like a Rolling Stone", "Positively 4th Street", and "I Want You" among others, along with the Bringing It All Back Home, Highway 61 Revisited and Blonde on Blonde albums, proved to be hugely influential on the development and popularity of folk rock. Although Dylan's move away from acoustic folk music served to outrage and alienate much of his original fanbase, his new folk rock sound gained him legions of new fans during the mid-1960s. The popularity and commercial success of the Byrds and Bob Dylan's blend of folk and rock music influenced a wave of imitators and emulators that retroactively became known as the folk rock boom.

Tom Wilson
Although he started out as a jazz musician, the young, African-American Columbia Records producer Tom Wilson became known as the "mid-wife of folk-rock" for his seminal work behind the scenes. As Bob Dylan's producer during the key transitional albums The Times They Are A-Changin, Another Side of Bob Dylan, and Bringing It All Back Home, he was a key architect of Dylan's electric sound. He is perhaps even better known, however, for first discovering Simon & Garfunkel at the tail end of the folk movement and then transforming them into folk-rock superstars with the unauthorized rock remix that made a number one hit out of their previously underappreciated song, "The Sound of Silence".

Other musicians

Music critic Richie Unterberger has noted that the commercial success of the Byrds' cover version of Dylan's "Mr. Tambourine Man", along with Dylan's own contributions to the genre on the albums Bringing It All Back Home, Highway 61 Revisited, and Blonde on Blonde, initiated an explosion of emulators and imitators. Their success led record producer Tom Wilson to add electric guitar, bass, and drums overdubs to "The Sounds of Silence", a song which had been recorded by the folk duo Simon & Garfunkel in 1964 and first released on their album Wednesday Morning, 3 A.M.. The reissued single rose to number 1 on the Billboard pop chart in late 1965, became a hit around the world, and set the duo on one of the most successful careers in pop and rock music. Simon and Garfunkel have been described as "folk-rock's greatest duo, and one whose fame and influence would persist well beyond folk-rock's heyday."

One of the first bands to craft a distinctly American sound in response to the British Invasion was the Beach Boys; while not a folk rock band themselves, they directly influenced the genre and at the height of the folk rock boom in 1966 had a hit with a cover of the 1920s West Indian folk song "Sloop John B", which they had learned from the Kingston Trio, who had learned it from the Weavers.

Much of the early folk-rock music emerged during a time of general global upheaval, the Vietnam War, and new concerns for the world by young people. In the United States, the heyday of folk rock was arguably between the mid-sixties and the mid-seventies, when it aligned itself with the hippie movement and became an important medium for expressing radical ideas. Cities such as San Francisco, Denver, New York City and Phoenix became centers for the folk rock culture, playing on their central locations among the original folk circuits. The "unplugged" and simplified sound of the music reflected the genre's connection to a critical view of a technological and consumerist society. Unlike pop music's escapist lyrics, arguably a fantasy distraction from the problems in life, folk artists attempted to communicate concerns for peace, global awareness, and other touchstones of the era. Bands whose music was significantly folk rock in sound during the mid-to-late 1960s included Donovan, the Lovin' Spoonful, the Mamas & the Papas, the Youngbloods, Love, and, in their early years, Jefferson Airplane.

In the mid-1960s, singer-songwriter Gordon Lightfoot began moving his folk songs into a folk-rock direction with recordings such as the percussion-driven "Black Day in July" about the 1967 Detroit riot. He would rise to top the charts in the 1970s with a number of his folk-rock recordings such as "Sundown" and "Carefree Highway" and eventually become known as a folk-rock legend. Some artists who originally produced with a harder edged rock sound found the ability to communicate more easily and felt more genuine in this method of delivery. In this category was Cat Stevens, who began in London much like the Byrds did in the United States but toned down the sound more frequently with acoustic instruments. He performed songs that contained concern for the environment, war, and the future of the world in general. The Canadian singer-songwriter Joni Mitchell won many Grammy Awards with her folk rock/pop songs.

British folk rock

British folk rock developed in Britain during the mid to late 1960s by the bands Fairport Convention, and Pentangle. It uses traditional British music and self-penned compositions in a traditional style, and is played on a combination of traditional and rock instruments. This incorporation of traditional British folk music influences gives British folk rock its distinctly British character and flavour. It evolved out of the psychedelia-influenced folk rock of British acts such as Donovan, the Incredible String Band, and Tyrannosaurus Rex, but was also heavily influenced by such American folk rock bands as the Byrds, Love, and Buffalo Springfield. British folk rock was at its most significant and popular during the late 1960s and 1970s, when, in addition to Fairport and Pentangle, it was taken up by groups such as Steeleye Span and the Albion Band.

Steeleye Span, founded by Fairport Convention bass player Ashley Hutchings, was made up of traditionalist folk musicians who wished to incorporate electrical amplification, and later overt rock elements, into their music. This, in turn, spawned the conspicuously English folk rock music of the Albion Band, a group that also included Hutchings. In Brittany folk rock was developed by Alan Stivell (who began to mix his Breton, Irish, and Scottish roots with rock music) and later by French bands like Malicorne. During this same period, folk rock was adopted and developed in the surrounding Celtic cultures of Ireland, Scotland, Wales, Brittany, and Cornwall, to produce Celtic rock and its derivatives.

Country folk

A subgenre originally arising from the early 1960s folk and country-influenced music of singer-songwriter artists such as Bob Dylan and Bobby Bare, as well as from folk revivalist vocal groups like the Kingston Trio. During the late 1960s, many folk rock artists including Dylan, Ian and Sylvia, and the Byrds began to incorporate a strong country influence into their music, drawing heavily on Hank Williams, Merle Haggard, and Buck Owens amongst others, resulting in the concurrent offshoot of country rock. This successful blending of country, folk and rock styles led to pioneering country folk records by folk-influenced singer-songwriters such as John Denver and Neil Young during the 1970s. Country folk music usually displays a softer, more "laid-back" feel than the majority of country music and is often complemented by introspective lyrics, thus preserving its folk singer-songwriter roots. Since the 1970s, the country folk subgenre has been perpetuated by artists including John Prine, Nanci Griffith, Kathy Mattea, Mary Chapin Carpenter, and Iris DeMent.

Celtic rock
A subgenre of folk rock that combines traditional Celtic instrumentation with rock rhythms, often influenced by a wide variety of pop and rock music styles. It emerged from the electric folk music of the late 1960s and was pioneered by bands such as Horslips, who blended Gaelic mythology, traditional Irish music and rock. The British singer-songwriter Donovan was also influential in developing Celtic rock during the late 1960s, with his albums The Hurdy Gurdy Man, Barabajagal, and Open Road, the latter of which actually featured a song entitled "Celtic Rock".

The subgenre was further popularised in 1973 by Thin Lizzy, who had a hit with "Whiskey in the Jar", a traditional Irish song performed entirely in the rock idiom. Throughout the 1970s, Celtic rock held close to its folk roots, drawing heavily on traditional Celtic fiddle, pipe, and harp tunes, as well as traditional vocal styles, but making use of rock band levels of amplification and percussion. In the 1980s and beyond, Celtic rock was perpetuated by bands such as the Pogues, the Waterboys, Runrig, Black 47, and the Prodigals. A more recent folk rock band based in England is the BibleCode Sundays. Celtic rock is also popular in Spain where bands such as Celtas Cortos have had a large following since the early 1990s.

Medieval folk rock
Medieval folk rock developed as a subgenre of electric folk from about 1970 as performers, particularly in England, Germany and Brittany, adopted medieval and renaissance music as a basis for their music, in contrast to the early modern and nineteenth century ballads that dominated the output of Fairport Convention. This followed the trend explored by Steeleye Span, and exemplified by their 1972 album Below the Salt. Acts in this area included Gryphon, Gentle Giant and Third Ear Band. In Germany Ougenweide, originally formed in 1970 as an acoustic folk group, opted to draw exclusively on High German medieval music when they electrified, setting the agenda for future German electric folk. In Brittany, as part of the Celtic rock movement, medieval music was focused on by bands like Ripaille from 1977 and Saga de Ragnar Lodbrock from 1979. However, by the end of the 1970s almost all of these performers had either disbanded or moved, like Gentle Giant and Gryphon, into the developing area of progressive rock. In the 1990s, as part of the wider resurgence of folk music in general, new medieval folk rock acts began to appear, including the Ritchie Blackmore project Blackmore's Night, German bands such as In Extremo, Subway to Sally or Schandmaul and English bands like Circulus.

Progressive folk rock
In Britain the tendency to electrify brought several progressive folk acts into rock. This includes the acoustic duo Tyrannosaurus Rex, who became the electric combo T. Rex. Others, probably influenced by the electric folk pioneered by Fairport Convention from 1969, moved towards more traditional material, a category including Dando Shaft, Amazing Blondel, and Jack the Lad, an offshoot of northern progressive folk group Lindisfarne, who were one of the most successful UK bands of the early 1970s. Examples of bands that remained firmly on the border between progressive folk and progressive rock were the short lived (but later reunited) Comus and, more successfully, Renaissance, who combined folk and rock with elements of classical music.

Folk metal
Folk metal is a fusion genre of heavy metal music and traditional folk music that developed in Europe during the 1990s. It is characterised by the widespread use of folk instruments and, to a lesser extent, traditional singing styles (for example, Dutch Heidevolk, Danish Sylvatica and Spanish Stone of Erech). It also sometimes features soft instrumentation influenced by folk rock.

The earliest folk metal bands were Skyclad from England, Cruachan from Ireland and Mago de Oz from Spain. Skyclad's debut album The Wayward Sons of Mother Earth was released in 1991 and would be considered a thrash metal album with some folk influences, unlike Cruachan's early work which embraced the folk element as a defining part of their sound. It was not until 1994 and 1995 that other early contributors in the genre began to emerge from different regions of Europe and beyond. Among these early groups, the German band Subway to Sally spearheaded a different regional variation that over time became known as medieval metal. Despite their contributions, folk metal remained little known with few representatives during the 1990s. It was not until the early 2000s when the genre exploded into prominence, particularly in Finland with the efforts of such groups as Finntroll, Ensiferum, Korpiklaani, Turisas, and Moonsorrow.

The music of folk metal is characterised by its diversity with bands known to perform different styles of both heavy metal music and folk music. A large variety of folk instruments are used in the genre with many bands consequently featuring six or more members in their regular line-ups. A few bands are also known to rely on keyboards to simulate the sound of folk instruments. Lyrics in the genre commonly deal with fantasy, mythology, paganism, history and nature.

title: Folk rock