I was surprised to see another thread about "Is this folk music?" People have been trying to define this for many years and have come to many very different conclusions. I think we should just agree to disagree. For anyone who's interested, here are some definitions. Perhaps one of them is correct.

-Music transmitted by mouth
-Music of the lower classes
-Music with unknown composers
-Old songs, with no known composers
-Music that has been transmitted and evolved by a process of oral transmission
-Music that originates in traditional popular culture or that is written in such a style
-Music, usually of simple character and anonymous authorship, handed down among the common people by oral tradition
-Music by known composers that has become part of the folk tradition of a country or region
-The music must be very old; that it is a particular style of music; that the author is not known. An art song is one that is written by a trained composer and is passed on in written form, whereas a folk song is one which is passed on in the oral tradition rather than in written form (Nettl & Myers, 1976).
-The International Folk Music Council adopted this definition at its Annual Conference in London in 1952. It is "music that has been submitted to the process of oral transmission. It is the product of oral transmission. It is the product of evolution and is dependent on the circumstances of continuity, variation and selection." The music may change and evolve as it passes from person to person (Karpeles, 1955, p. 6-7).
-The music also has a simple melody. Brand (1962) described the American folk song as "distinguishable by a special sound, a kind of 'simple' noise" (p. 10).
-Rhodes (1966) said that folk music could be defined by its sociological function because it is a kind of social behavior. "Interpreted in this light, it can reveal a great deal regarding the interests, thinking and feeling of the people" (Rhodes, 1966, p. 18).
-Bohlman (1988) talked about folk music's ability to "express the most profound of human values" (p. xii).
-Historically, both folk and popular music are learned through hearing and performing, but that performers of "serious" music have formal training in music theory, composition, and more (Denski, 1992).
-There are two kinds of popular music, the folk and mass forms. The folk form is performed live, and the mass form is recorded (Cutler, 1985)
-Forcucci wrote in 1984 that:
1. Folk songs represent the musical expressions of the common people. 2. These songs are not composed in that they are not the works of skilled, tutored musicians. It is more accurate to say that they have been created rather than composed.
3. These songs are ordinarily the product of an unknown person or group of persons. The credits often read: Anonymous; American Folk Song; Traditional; or Southern Mountain Song. [But Forcucci notes that   there are folklike songs where the author is known, but that these songs are "patterned to fit the mold of what typical American folk songs should sound like," p. 18.]
4. The words or lyrics of folk songs are usually colloquial in nature to reflect the speech patterns and expressions of a particular people or region.
5. These songs are highly singable, primarily because they were first presented with the singing voice rather than have been written down in musical notation beforehand.
6. Folk songs are simply structured, both musically and verbally. It is their naivete that gives them their charm.
7. These songs can be effectively performed without instrumental accompaniment. When they are accompanied, a less formal instrument (such as a guitar, banjo, accordion, dulcimer, or Autoharp) is considered appropriate.
8. Folk songs are indigenous to a particular region or people because they reflect the musical/verbal preferences of that people or region in their materials. (Forcucci, 1984, pp. 18-19)
-Folk music is a vital, living art, not an archeological antiquity. It continues to be a medium through which the people express their thoughts, feelings and interests even as the folk did in the past. The subject matter and the musical style have changed with the changing times, but the fundamental principle of folk song and its relation to the people have remained the same. (Rhodes, 1966)
-Michael Cooney's definition can be found at Michael Cooney's definition
-Michael also said, in a less scholarly moment, "If it takes more than two trips to get your gear from the car to the stage, it ain't folk music."
-Catfish Willie said, "It's a four letter word that starts with F and ends with K and if you use it, they won't play your songs on the radio."
-Perhaps the most famous definition of folk music is Big Bill Broonzy's - I guess all songs is folk songs. I never heard no horse sing 'em.
-There has been an ongoing debate about the definition of folk music going on in the pages of Sing Out! magazine, starting in the early 50s and going on to the present.