- Edited
[deleted] jawkins
It occurred to me that this technology couldn't possibly exist to the layman. Everything recorded in a studio has a different track for each dub/instrument even back to the day of vacuum tubes and analog. Only the record company/engineer could isolate the tracks. They own it. There's no profit to make selling a bass track, for example, to the general public. These stems as you call them probably do originate from the studio and a royalty is paid by Rock Band. By the time it is MP4 or other, it is a wholly compressed file anyway so unworkable.
This ^^^ entire paragraph is 100% speculation on my part, but seems likely the truth or close to it, whatever the truth may be regarding acquiring a particular drum track, vocal etc.
****Footnote. There are craploads of guitar players and drummers on youtube playing over an existing (copyrighted) song with a their particular instrument stripped out. A guy playing Eddie Van Halen over a guitar-less "Running With The Devil" for example. So we know some technology exists to us peons that can strip out a single track...so everything I wrote up to now is invalidated. But what becomes of the single missing track? Can I have it?
edit...unless ALL the youtubers above are using rock band?