How to exploit the possibilites of blockchain for proof of authorship?
If expressing the (artistic) work in any kind of document (be it sheets, photos or audio/video recording) is good enough, then you can use something called proof of existence. This simple method allows you to store a hash of any document into the Blockchain, thus proving it existed at the time when a particular block was mined.

You can indlude the autor's name (or other identifier) into the document, making it clear that he (at least) knew about it back then. If nobody proves the possesion/familiarity with that particular file/work dated before, the author should be able to claim his rights.

One (perhaps the first) proof-of-existence service is proofofexistence.com.