There was an awful lot of great variety and originality in music in the few centuries before music copyright was enforced as strongly as it is today. Mozart, among others, did make a lot of derivative music but much of that was (and still is) earth-shatteringly fantastic, like most art (and code for that matter) that builds on existing work.
Popular music would survive very well with much reduced copyright laws in the same way that fashion survives today. Jungle -> Drum and Bass -> Grime -> Dubstep, no one wants to listen to the previous trend - pay for access to the latest, pay for it as it comes out, pay for concerts and live events - there are lots of models that would leave music thriving if publishing rights went away tomorrow.
Popular music would survive very well with much reduced copyright laws in the same way that fashion survives today. Jungle -> Drum and Bass -> Grime -> Dubstep, no one wants to listen to the previous trend - pay for access to the latest, pay for it as it comes out, pay for concerts and live events - there are lots of models that would leave music thriving if publishing rights went away tomorrow.