Unfortunately, topsie, there appears to be a copyright on silent tracks; that's if you take notice of the art music world and their publishers. As one who started out unaccompanied and then got into uninstrumented harmonies and only later started playing (and singing) with instruments I note your first phrase.

But I was thinking along the lines of selecting items we could sing (or play) with those backings done by others that we would like to have.

Cheers, Rowan