Is this too unrealistic to expect? Has something like this been tried before?
Plenty of other artists have as well, but this is the most high profile example I can think of. I agree it would be great if it happened more often.
The beatles multi-tracks are also available (although they were only recorded 4-track so not every instrument always has it's own track), and there has been a handful of artists who have released their samples of one song for remix competitions (Daft Punk, Royksopp, Booka Shade).
1. People would use the tracks to create custom remixes which they would then distribute. What happens when a remix becomes more popular than the original track? Artists generally have to pay other artists to remix their songs (usually via royalties).
2. Creativity. When an artist creates something they want you to hear it the way it was intended. Allowing you to remix it however you like takes away a lot of the creative control from the artist.
And another important remark: some artists are flattered when someone asks them to make a remix for their song. (Imagine you're an artist and your idol asks you to make a remix of his song.)
I write music and have considered releasing separate tracks so people can freely remix it but I prefer just having mixes that are controlled by me. Allowing another artist you know to remix your track still allows you some sort of control (you know their style so have some idea of how the remix will go). Giving up that control is a big step and, I think, an unnecessary one.
Why do you need that control? Someone creating something new with your work, doesn't seem to damage your work in any way.
Closest I've found is to take the .mogg files out of the Guitar Hero games and use those to make new mixes. :-)
Of course, you can very easily get just the vocal track by subtracting the two. Sometimes the "non-vocal" track will still include backing vocals or the like in appropriate places, and just pull out the main vocal track.
Some musicians have even released every single track of their work separately; see "Desperate Religion" on http://en.wikipedia.org/wiki/Trilogy_(ATB_album) , intentionally inviting remixes.
For music where the vocal tracks aren't released separately, you can often pull them out nevertheless. The best is if you can get the audio in 5.1 -- vocals are almost always center-panned, which makes extracting them quite easy.
And when you have them, just use something in the like of Ableton Live and that will be it. I think that that's what you mean right?
It will be a great idea to have tracks released as several `layers` so that the user can choose which of them to play and which not, for example the bass/beats layer, layer with melodies, layer with the percussions, layer with the vocals of course, but that sounds like semi-studio production.