Many you will know that before Led Zeppelin formed in 1968 John Paul Jones was a session bassist and arranger for British pop and rock music, his work appearing on tracks like Donovan's "Mellow Yellow." Which brings up the obvious question of whether he did any work for the library labels. Discogs doesn't have any references, but library recordings usually only list the composer's name. Jimmy Page was of course also a session musician, but I think it's less likely he was involved in library music recordings because he didn't read music.