Jazz is a construct. Nothing can be called jazz simply because of its ‘nature’. Musical genres such as the military march, opera and reggae are relatively homogeneous and easy to identify. By contrast, the term jazz is routinely applied to musics that have as little in common as an improvisation by Marilyn Crispell and a 1923 recording by King Oliver and his Creole Jazz Band. Developed well outside the more carefully regulated institutions of American culture, early jazz, proto-jazz or Ur-jazz was performed by people from an extremely wide variety of backgrounds. Many styles of playing were mixed together and others were split off and acquired different names. If today we call something jazz, it has much more to do with the utterances of critics, journalists, record companies and club owners than with the music itself.

Those who have been most devoted to defining the music and to discriminating between true jazz and false jazz often rely upon tautologies and ad hominem arguments. The esteemed poet and jazz writer Philip Larkin, for example, once wrote: