Very interesting, David. Another example is the music of the Beatles. If you listen to them record take after take of one song, you discover how hard they worked on them, how sometimes they were crap, how the 'best' take they decided to release could just as easily be the 22nd take as the 2nd take (or combine bits of different takes). And one of the best bootleg CDs I've got is of Dylan recording Like a Rolling Stone. Same thing, except here he and the band build up to the take that was actually released. It's such a fascinating process that the critic Greg Marcus even wrote a book about this one bootleg CD.