It is a matter of fact that musical genres exist in many cultures. Nineteenth century positivist musicologists even treated them (or what was then conceived as genres) as living entities. Such biological metaphors – implying concepts of birth, infancy, growth, maturity, death – were soon abandoned, in the wake of the hegemony of formalist musicology, and its devaluation of any concept related to function, context, community. Genres, however, continued to survive and are still flourishing: their existence today found in the domains of culture, of commonsense, that is, in the semiosphere, in the discourses and practices of musicians, critics, fans, concert promoters, record industry executives, sales people, web designers, and so on. One of the main challenges for scholars is to relate such existences to an understanding of the meaning and working of music taxonomies: ethnographies are useful, but without theory they are blind. [1]

As cultural units (and not metaphysical categories), genres are rooted in history: which would imply that for each genre that comes to our mind there must have been a time when it didn't yet exist. This might be an obvious observation, but one that does not seem to have troubled many of the scholars who have dealt with the subject. On the contrary, I believe that no genre theory – be it a 'strong' theory or a simple description of how the concept is used in contemporary communities – can be valid if it doesn't take genre formation and diachronic processes into consideration.

According to several theoretical approaches, which, in my view, should be seen to overlap and/or complement (rather than contradict and oppose) each other, the 'birth' of a genre can be located in the establishment of conventions within a community, in the 'semiotic act' of naming, as well as in the acknowledgement of 'family resemblances', in the acceptance of prototypes. Such processes, however, do not take place in a void, but within a system or network of existing genres: this also implies that some or all of them can be activated, or catalysed, or polarized by existing genres, to which the new genre is opposed, or put on their side as a variant. For example: is popular music a genre? According to colloquial usage and to some definitions, yes, but when referring to it as a superordinate category, which includes many genres, one may prefer to call it a type of music. Also, in discourses where distinctions between genre and style are not relevant, type may be a useful synonym for both.