When dealing with American popular music, one comes across patterns of fast and systematic change and evolution. Contrarily to classical music, or even jazz, where change is accounted for on artistic grounds, stressing the individuality of the artist's inspiration, it is most of the time by economic and marketing reasons that the transformation of popular music is justified, by the almost scientifically engineered fickleness of the popular market.

But such explanations do not exhaust the issue,  nor do they address the central notion of creativity. In the realm of American rock/pop music, a particularly rich field, product rotation is unusually high. Can it be imputed only to the marketing genius of a handful of entrepreneurs? Is there such a thing as progress in music? How can we account for the emergence of new sounds?

What happens to older ones? Could there be a modelizable principle?

Such questions may appear purely rhetorical in view of the magnitude of the task, mere mental speculations bound to remain unanswered. However, attempts have been made to provide explanations others than merely economic, though nevertheless incorporating the historical and social context in which the creative process takes place. Researchers have come forward with several theories and we would like to concentrate on two of them currently favoured by the rock academia: the "revolutionary" principle, and the "misreading" model, particularly as their relevance may reach beyond the realm of rock music.

Early explanations used a model borrowed from 19th century physical science (namely the 2nd law of thermodynamics). Taken up by popular culture specialist John Fiske or subcultures analyst Dick Hebdige, it interpreted evolution as resulting from the gradual acceptance by the majority of unconventional codes. Evolution was thus equated to conventionalization. If theoretically such a model is neither positive nor negative, it is nevertheless often described as a degenerative process (Hebdige talks of Bowdlerization). What was originally pure, authentic, "artistic" becomes fake, commercial, artificial.

In music, it was often presented as a downward spiral from black to white genres: hot jazz degenerating into swing, Rhythm & Blues into Rock & Roll, Rock & Roll into pop, etc. The newer form was seen as lacking an essential element that had characterized the originator, whether it be the art of syncopation, rebelliousness, or sexuality. A unilateral exchange had occured which, to sustain popularization, had deprived the original genre from its substance, giving birth to an empty, plagiaristic form (in Michael Jarret's words, a "semiotic diaspora", 169).