The music industry needs to more widely use some kind of equivalent to the ISBN that the book industry uses. A simple "ISMN" list per playlist/library would be all that would be needed to move between services when both apps have the same songs.
One could also imagine a standardized ismn://<number> URL format that could open in your preferred music app, and this could work even without a streaming service if you already own that song in your personal music collection.
But, I've never actually seen it used for recordings; it seems to be focused solely on music notation. So, it would be nice to have some kind of recording-focused identifier for keeping track of specific performances between services.
It's a pity that compression is likely to provide subtly different data under different network conditions. If everything were lossless we could just use hashes as identifiers and proceed without the participation of the apps.
After all, they have no incentive to make this easy for us.
This is actually a beautiful idea. It'd definitely be possible for music purchased through bandcamp since lossless is generally available for most releases. Commenting to bookmark this.
Content addressable doesn't really work here... different apps may have the same recordings encoded in different formats and bitrates, but they are still the same recording. Unless you meant "content addressable" in the sense of a uniquely assigned identifier like I was already talking about, and not a computed identifier from the raw bytes of the file like a hash.
This sounds like an acoustic fingerprint, such as AcoustID[0]. I think AcoustIDs and XSPF[1] would be a good combination for shared playlists. It's a shame that development stopped on the Tomahawk music player[2], it would have been an ideal platform for shared playlists like this.
One could also imagine a standardized ismn://<number> URL format that could open in your preferred music app, and this could work even without a streaming service if you already own that song in your personal music collection.
ISMN seems to exist: https://www.loc.gov/ismn/about.html
But, I've never actually seen it used for recordings; it seems to be focused solely on music notation. So, it would be nice to have some kind of recording-focused identifier for keeping track of specific performances between services.