Sure you can hold only a hash. But this way opens also a wide array of possible abuses (linking to top hits, taking fees for non playable media and many more; most can be mitigated, but still no ideal solution). Keeping data in chain or in chain-like structure layered on chain provides paradoxically means to evade accusations from top labels - this way one can safeguard own creation in best way possible.
So, again, no good solution solving all issues, either with storing hash or full data.
Connecting bc to real world solution is still far from being realistic and reliable - in large scale of course. Because bc has inherent drawbacks that block wide adoption.