The time-stamping use case you describe is basically non-existent. Even light media like images are not stored on-chain 99.99% of the time. Time-stamping a URL

The time-stamping use case you describe is basically non-existent. Even light media like images are not stored on-chain 99.99% of the time. Time-stamping a URL to an audio track that is hosted on a server you own is not in itself a prove of the existence of this copyrighted material. I have seen interesting on-chain visual experiments (generative animation fully stored on-chain) but that trend seems to have faded under the pressure of the NFT monetization spike+burst.