Categorising music, especially into finer genres or sub genres,
can be difficult for newly emerging styles or for pieces
of music that incorporate features of multiple genres.
Attempts to pigeonhole particular musicians in a single genre
are sometimes ill-founded as they may produce music in a variety
of genres over time or even within a single piece.
Some people feel that the categorisation of music into genres is
based more on commercial and marketing motives than musical criteria.
John Zorn, for example, a musician whose work has covered a
wide range of genres, wrote in Arcana: Musicians on Music that genres are tools
used to commodify and commercialise an artist's complex personal vision.