Just a semantic thing, but it is still prior art... it's just probably not prior art that, on its own, is enough to invalidate these claims. It could still be relevant for obviousness purposes.
I know I happily streamed .au music from the sounds.sdsu.edu FTP server into /dev/audio (late at night, of course) in that era. Since it was an FTP server, I suppose there was a rough sort of DRM (maximum connections allowed) and metadata (directories and filenames describing the artist and song name). Even though I had seen a good deal of MBONE broadcasts, it was quite a novelty to hear a song streamed on demand.
Fair enough, but given almost any thought at that time, we'd have thought of metadata (probably not DRM because we wouldn't have believed something so stupid was needed).
Once you've got a network, walkmans, a "mic" input, and a speaker, this stuff is obvious and that's the point.
Two things would need to be present -- DRM of some sort. And music metadata.
These are two things that I suspect Spotify makes use of. I suspect you probably didn't at St Andrews for your streaming, but let me know if you did.