Folk music, in the original sense of the term, is music by and of the people. Folk music arose, and best survives, in societies not yet affected by mass communication and the commercialization of culture. It normally was shared and performed by the entire community (not by a special class of expert performers), and was transmitted by word of mouth.
During the 20th century, the term folk music took on a second meaning: it describes a particular kind of popular music which is culturally descended from or otherwise influenced by traditional folk music. Like other popular music, this kind of folk music is most often performed by experts and is transmitted in organized performances and commercially distributed recordings. However, popular music has filled some of the roles and purposes of folk music where it has replaced it.

Defining folk music

"Folk music is usually seen as the authentic expression of a way of life now past or about to disappear (or in some cases, to be preserved or somehow revived). Unfortunately, despite the assembly of an enormous body of work over some two centuries, there is still no unanimity on what folk music (or folklore, or the folk) is." (Middleton 1990, p.127)
Gene Shay, co-founder and host of the Philadelphia Folk Festival, defined folk music in an April 2003 interview by saying: "In the strictest sense, it's music that is rarely written for profit. It's music that has endured and been passed down by oral tradition [...] And folk music is participatory—you don't have to be a great musician to be a folk singer. [...] And finally, it brings a sense of community. It's the people's music."
The English term folk, which gained usage in the 18th century (during the Romantic period) to refer to peasants or non-literate peoples, is related to the German word Volk (meaning people or nation). The term is used to emphasize that folk music emerges spontaneously from communities of ordinary people. "As the complexity of social stratification and interaction became clearer and increased, various conditioning criteria, such as 'continuity', 'tradition', 'oral transmission', 'anonymity' and uncommercial origins, became more important than simple social categories themselves."
Charles Seeger (1980) describes three contemporary defining criteria of folk music (Middleton 1990, p.127-8):
1. A "schema comprising four musical types: 'primitive' or 'tribal'; 'elite' or 'art'; 'folk'; and 'popular'. Usually...folk music is associated with a lower class in societies which are culturally and socially stratified, that is, which have developed an elite, and possibly also a popular, musical culture." Cecil Sharp (1972), A.L. Lloyd ().
2. "Cultural processes rather than abstract musical types...continuity and oral transmission...seen as characterizing one side of a cultural dichotomy, the other side of which is found not only in the lower layers of feudal, capitalist and some oriental societies but also in 'primitive' societies and in parts of 'popular cultures'." Redfield (1947) and Dundes (1965).
3. Less prominent, "a rejection of rigid boundaries, preferring a conception, simply of varying practice within one field, that of 'music'."

The appeal of folk music

The appeal of folk music is distinct from that of classical or popular music. Typically, folk music lacks the technical sophistication and complexity that is often found in classical music and (to a lesser extent) in popular music. Yet the musical inventiveness of ordinary people, especially when acting together in a tight-knit musical community, has resulted in works of folk music often experienced by modern listeners as extraordinarily beautiful or stirring. A particular virtue that often stands out in folk music is its purity: it often obtains exceptional aesthetic results from the simplest of musical means.

Subjects of folk music

Apart from instrumental music that forms a part of folk music, especially dance music traditions, much folk music is vocal music Vocal music is music intended for performance mainly by singers. Other musical instruments may be involved, but the choir is the main focus of the piece. Examples of vocal music include choral music, yodeling, Sacred Harp, and Barbershop, since the instrument that makes such music is usually handy. As such, most folk music has lyrics, and is about something.
Narrative verse looms large in the folk music of many cultures. This encompasses such forms as traditional epic poetry, much of which was meant originally for oral performance, sometimes accompanied by instruments. Many epic poems of various cultures were pieced together from shorter pieces of traditional narrative verse, which explains their episodic structure and often their in medias res plot developments. Other forms of traditional narrative verse relate the outcomes of battles and other tragedies or natural disasters. Sometimes, as in the triumphant Song of Deborah found in the Biblical Book of Judges, these songs celebrate victory. Laments for lost battles and wars, and the lives lost in them, are equally prominent in many folk traditions; these laments keep alive the cause for which the battle was fought. The narratives of folk songs often also remember folk heroes such as John Henry to Robin Hood. Some folk song narratives recall supernatural events or mysterious deaths.
Hymns and other forms of religious music are often of traditional and unknown origin. Western musical notation was originally created to preserve the lines of Gregorian chant, which before its invention was taught as an oral tradition in monastic communities. Folk songs such as Green grow the rushes, O present religious lore in a mnemonic form. In the Western world, Christmas carols and other traditional songs preserve religious lore in song form.
Other sorts of folk songs are less exalted. Work songs are composed; they frequently feature call and response structures, and are designed to enable the labourers who sing them to coordinate their efforts in accordance with the rhythms of the songs. In the armed forces, a lively tradition of jody calls are sung while soldiers are on the march. Love poetry, often of a tragic or regretful nature, prominently figures in many folk traditions. Nursery rhymes and nonsense verse also are frequent subjects of folk songs.

Variation in folk music

Music transmitted by word of mouth though a community will, in time, develop many variants, because this kind of transmission cannot produce word-for-word and note-for-note accuracy. Indeed, many traditional folk singers are quite creative and deliberately modify the material they learn.
Because variants proliferate naturally, it is naïve to believe that there is such a thing as the "authentic" version of a ballad such as "Barbara Allen." Field researchers in folk song (see below) have encountered countless versions of this ballad throughout the English-speaking world, and these versions often differ greatly from each other. None can reliably claim to be the original, and it is quite possible that whatever the "original" was, it ceased to be sung centuries ago. Any version can lay an equal claim to authenticity, so long as it is truly from a traditional folksinging community and not the work of an outside editor.
Cecil Sharp had an influential idea about the process of folk variation: he felt that the competing variants of a folk song would undergo a process akin to biological natural selection: only those new variants that were the most appealing to ordinary singers would be picked up by others and transmitted onward in time. Thus, over time we would expect each folksong to become esthetically ever more appealing — it would be collectively composed to perfection, as it were, by the community.
On the other hand, there is also evidence to support the view that transmission of folk songs can be rather sloppy. Occasionally, collected folk song versions include material or verses incorporated from different songs that makes little sense in its context. A perfect process of natural selection would not have permitted these incoherent versions to survive.
The decline of folk traditions in modern societies
Folk music seems to reflect a universal impulse of humanity. No fieldwork expedition by cultural anthropologists has yet to discover a preindustrial people that did not have its own folk music. It seems safe to infer that folk music was a property of all people starting from the dawn of the species.
However, the development of modern society--first literacy, then the conversion of culture into a salable commodity--created a new form of transmission of music that first influenced, then in some societies essentially eliminated the original folk tradition. The decline of folk music in a culture can be followed through three stages.

Stage I: Urban influence

One of the first folk traditions impacted by modern society was the folksong of rural England. Starting in Elizabethan times, urban poets wrote broadsheet ballads that (thanks to printing) could be sold widely. The ballads probably didn't need musical notation, since they would have been sung to tunes that everybody knew, the folk tradition being very much alive at the time. These ballads heavily influenced the folk tradition, but did not override it. In fact, the folk tradition showed great resilience. Through the process of folk transmission, the urban ballads were modified, keeping the more vivid content and ironing out the less "citified" material. The resulting body of folk lyrics is widely considered to be a very appealing blend. Thus, the printing press and widespread literacy did not suffice to destroy the English folk tradition, but in some ways enriched it.
The English folk song legacy was probably affected by urban melodies as well as words. The clue here is that folk music in remote rural areas of the English-speaking world, such as Highland Scotland or the Appalachian mountains, abounds in tunes that employ the pentatonic scale, a scale widely used for folk music around the world. However, pentatonic music was rare among the rural English villagers who first volunteered their tunes to researchers in the late 19th century. A plausible explanation is that life in rural England was far more closely affected by the proximity to the urban centers. Music in the standard major and minor scales evidently penetrated to the nearby rural areas, where it was converted to folk idiom, but nevertheless succeeded in displacing the old pentatonic music.

Stage II: Replacement of folk music by popular music

The pattern of urban influence on folk music was intensified to outright destruction as soon as the capitalist economic system had developed to the point that music could be packaged and distributed for the purpose of earning a profit--in other words, when popular music was born. It was around Victorian times that ordinary people of the Western world were first offered music as a mass commodity, for example, in the phenomenon of Music Hall.
The introduction of popular music was simultaneous with the latter part of the Industrial Revolution. This was a time of great change in lifestyle for the great body of the people, notably the migration of the old agrarian communities to the new industrial ones. It is likely that the resulting social disruption helped cut people's emotional bonds to their old folk music, and thereby helped the shift in taste toward popular music.
As technology advanced, succeeding generations became enticed with popular music in ever more accessible and desirable forms. Gramophone records became LPs and then CDs; the Music Hall gave way to radio, followed by television. With the ever-increasing success of popular music, the musical life of many individuals eventually ceased to include any folk music at all. Moreover, since popular music for most people is passive music (that is, listened to, but not created or performed), the overwhelming success of popular music also entailed a sharp decline of music as an active, participatory activity.

Stage III: Loss of musical ability in the community

The terminal state of the loss of folk music can be seen in the United States and a few similar societies, where except in isolated areas and among hobbyists, traditional folk music no longer survives. In the absence of folk music, many individuals do not sing. It is possible that non-singers feel intimidated by widespread exposure in recordings and broadcasting to the singing of skilled experts. Another possibility is that they simply cannot sing, because they did not sing when they were small children, when learning of skills takes place most naturally. Certainly it is very common for contemporary Americans to claim that they cannot sing.
There is anecdotal evidence that the loss of singing ability is continuing rapidly at the present time. As recently as the 1960's, audiences at American sporting events collectively sang the American national anthem before a game; the anthem is now generally assigned to a recording or to a soloist.
Inability to sing is apparently unusual in a traditional society, where the habit of singing folk song since early childhood gives everyone the practice needed to able to sing at least reasonably well.

Regional variation

The loss of folk music is occurring at different rates in different regions of the world. Naturally, where industrialization and commercialization of culture are most advanced, so tends to be the loss of folk music. Yet in nations or regions where folk music is a badge of cultural or national identity, the loss of folk music can be slowed; this is held to be true, for instance in the case of Ireland, Brittany, and Galicia, all of which retain their traditional music to some degree.
Fieldwork and scholarship on folk music
Starting in the 19th century, interested people - academics and amateur scholars - started to take note of what was being lost, and there grew various efforts aimed at preserving the music of the people. One such effort was the collection by Francis James Child in the late 19th century of the texts of over three hundred ballads in the English and Scots traditions (called the Child Ballads). Contemporaneously came the Reverend Sabine Baring-Gould, and later and more significantly Cecil Sharp who worked in the early 20th century to preserve a great body of English rural folk song, music and dance, under the aegis of what became and remains the English Folk Dance and Song Society (EFDSS). Sharp also worked in America, recording the folk songs of the Appalachian Mountains in 1916-1918 in collaboration with Maud Karpeles and Olive Dame Campbell.
Around this time, composers of classical music developed a strong interest in folk song collecting, and a number of outstanding composers carried out their own field work on folk song. These included Ralph Vaughan Williams in England and Béla Bartók in Hungary and neighboring countries. These composers, like many of their predecessors, incorporated folk material into their classical compositions.
In America, during the 1930s and 1940s, the Library of Congress worked through the offices of musicologist Alan Lomax and others to capture as much American field material as possible.
Often, fieldworkers in folk song hoped that their work would restore folk music to the people. For instance, Cecil Sharp campaigned, with some success, to have English folk songs (in his own heavily edited and expurgated versions) to be taught to schoolchildren.
One theme that runs through the great period of scholarly folk song collection is the tendency of certain members of the "folk", who were supposed to be the object of study, to become scholars and advocates themselves. For example, Jean Ritchie was the youngest child of a large family from Viper, Kentucky that had preserved many of the old Appalachian folk songs. Ritchie, living in a time when the Appalachians had opened up to outside influence, was university educated and ultimately moved to New York City, where she made a number of classic recordings of the family repertoire and published an important compilation of these songs.

Folk revivals

As folk traditions decline, there is often a conscious effort to resuscitate them. Such efforts are often exerted by bridge figures such as Jean Ritchie, described above. Folk revivals also involve collaboration between traditional folk musicians and other participants (often of urban background) who come to the tradition as adults.
The folk revival of the 1950's in Britain and America had something of this character. In 1950 Alan Lomax came to Britain, where at a Working Men's Club in the remote Northumberland mining village of Tow Law he met two other seminal figures: A.L.'Bert' Lloyd and Ewan MacColl, who were performing folk music to the locals there. Lloyd was a colourful figure who had travelled the world and worked at such varied occupations as sheep-shearer in Australia and shanty-man on a whaling ship. MacColl, born in Salford of Scottish parents, was a brilliant playwright and songwriter who had been strongly politicised by his earlier life. MacColl had also learned a large body of Scottish traditional songs from his mother. The meeting of MacColl and Lloyd with Lomax is credited with being the point at which the British roots revival began. The two colleagues went back to London where they formed the Ballads and Blues Club which eventually became renamed the Singers' Club and was the first, as well as the most enduring, of what became known as folk clubs. As the 1950s progressed into the 1960s, the folk revival movement built up in both Britain and America.

The emergence of popular folk artists

During the twentieth century, a crucial change in the history of folk music began. Folk material came to be adopted by talented performers, performed by them in concerts, and disseminated by recordings and broadcasting. In other words, a new genre of popular music had arisen. This genre was linked by nostalgia and imitation to the original traditions of folk music as it was sung by ordinary people. However, as a popular genre it quickly evolved to be quite different from its original roots.
Confusingly, popular (i.e., commercially-disseminated) music based on a folk tradition is called "folk music", no matter how different it may be from a folk music rooted in the community. As a result, some individuals in a modern society are unaware that folk music of the original variety ever existed.
The rise of folk music as a popular genre began with performers whose own lives were rooted in the authentic folk tradition. Thus, for example, Woody Guthrie began by singing songs he remembered his mother singing to him as a child. Later, in the 1930s and 1940s, Guthrie both collected folk music and also composed his own songs, as did Pete Seeger, who was the son of a professional musicologist. Through dissemination on commercial recordings, this vein of music became popular in the United States during the 1950s, through singers like the Weavers (Seeger's group) and the Kingston Trio, who tried to reproduce and honor the work that had been collected in preceding decades. The itinerate folksinger lifestyle was exemplified by Ramblin' Jack Elliott, a disciple of Woody Guthrie who in turn influenced Bob Dylan. Sometimes these performers would locate scholarly work in libraries and revive the songs in their recordings, for example in Joan Baez's rendition of "Henry Martin," which adds a guitar accompaniment to a version collected and edited by Cecil Sharp.
Many of this group of popular folk singers maintained an idealistic, leftist/progressive political orientation. This is perhaps not surprising. Folk music is easily identified with the ordinary working people who created it, and preserving treasured things against the claimed relentless encroachments of capitalism is likewise a goal of many politically progressive people. Thus, in the 1960s such singers as Joan Baez, Phil Ochs and Bob Dylan followed in Guthrie's footsteps and to begin writing "protest music" and topical songs, particularly against the Vietnam War, and likewise expressed in song their support for the civil rights movement. Such songs were newly written, but took their instrumentation and stanza forms from folk tradition.
In Ireland, The Clancy Brothers & Tommy Makem (although the members were all Irish born, the group became famous while based in New York's Greenwich Village, it must be noted), The Dubliners, Clannad, Planxty, The Chieftains, The Pogues and a variety of other folk bands have done much over recent years to revitalise and repopularise Irish traditional music. These bands were rooted, to a greater or lesser extent, in a living tradition of Irish music, and they benefitted from collection efforts on the part of the likes of Seamus Ennis and Peter Kennedy, among others.

The blending of folk and popular genres

The experience of the last century suggests that as soon as a folk tradition comes to be marketed as popular music, its musical content will quickly be modified to become more like popular music. Such modified folk music often incorporates electric guitars, drum kit, or forms of rhythmic syncopation that are characteristic of popular music but were absent in the original.
One example of this sort is contemporary country music, which descends ultimately from a rural American folk tradition, but has evolved to become vastly different from its original model. Rap music evolved from an African-American inner-city folk tradition, but is likewise very different nowadays from its folk original. A third example is contemporary bluegrass, which is a modified development of American old time music.
As less traditional forms of folk music gain popularity, one often observes tension between so-called "purists" or "traditionalists" and the innovators. For example, traditionalists were indignant when Bob Dylan began to use an electric guitar. His electrified performance at the 1965 Newport Folk Festival was to prove to be an early focal point for this controversy.
Sometimes, however, the exponents of amplified music were bands such as Fairport Convention, Pentangle and Steeleye Span who saw the electrification of traditional musical forms as a means whereby to reach a far wider audience, and their efforts have been largely recognised for what they were by even some of the most die-hard of purists.
Since the 1970s a genre of "contemporary folk", fuelled by new singer-songwriters, has continued to make the coffee-house circuit and keep the tradition of acoustic non-classical music alive in the United States. Such artists include Steve Goodman, John Prine, Cheryl Wheeler, Bill Morrisey, and Christine Lavin. Lavin in particular has become prominent as a leading promoter of this musical genre in recent years. Some, such as Lavin and Wheeler, inject a great deal of humor in their songs and performances, although much of their music is also deeply personal and sometimes satirical.
Traditional folk music forms also merged with rock and roll to form the hybrid generally known as folk rock which evolved through performers such as The Byrds, Simon and Garfunkel, The Mamas and the Papas, and many others. More recently the same spirit has been embraced and expanded on by performers such as Ani Difranco. At the same time, a line of singers from Baez to Phil Ochs have continued to use traditional forms for original material.
A similar stylistic shift, without using the "folk music" name, has occurred with the phenomenon of Celtic music, which in many cases is based on an amalgamation of Irish traditional music, Scottish traditional music, and other traditional musics associated with lands in which Celtic languages are or were spoken (regardless of any significant research showing that the musics have any genuine genetic relationship; so Breton music and Galician music are often included in the genre).
Folk music is still extremely popular among some audiences today, with folk music clubs meeting to share traditional-style songs, and there are major folk music festivals in many countries, eg the Port Fairy Folk Festival is a major annual event in Australia attracting top international folk performers as well as many local artists.