This is Chris Cutler's poignant phrase, from File Under Popular (November Books, 1985), which also includes a good analysis of attemped definitions of popular music, and a definition of folk music integral to the use of that term in Plunderphonics:
First, the medium of its musical generation and perpetuation is tradition and is based in human, which is to say biological, memory. This mode centers around the ear, and can exist only in two forms: as sound and as memory of sound.
Second, the practice of music is in all cases an expressive attribute of a whole community which adapts and changes as the concerns and realities it expresses--or as the vocabulary of the collective aesthetic--adapt and change. There is no other external pressure upon it.
Third, there can be no such thing as a finished or definitive piece of music. At most there could be said to be "matrixes" or "fields." Consequently, there is also no element of personal property, though there is of course individual contribution. (File Under Popular, pp. 133-4.)