Ok my 2 sats:

You can prove you've made any individual original piece by producing a cryptographic signature of the original file, although I'm still not sure how this could be translated into a decentralised reward mechanism without opening security/legality issues though.

Centralisation does suck, but I'm having extreme trouble wrapping my head around an actually decentralised way to do so without screwing up the blockchain. It may be a huge job, but perhaps new tx types, like Namecoin uses for name_new, name_firstupdate etc...

Just spitballing ideas, could we integrate some kind of decentralised voting mechanism for reward of artists? This could integrate with the in-wallet player concept nicely at least - people can upload files and signatures, but unless it gets majority-voted it'll get pruned perhaps? Obviously there is room for abuse, but if the network is strong enough (perhaps we open up staking when people are playing music or something) then it should be able to withstand it.