Was thinking about songs on albums that were demoed or played live prior to the completion of a previous album. In other words, the song existed in some form and could have made it on a previous album, but not counting something that was only worked between releases (e.g. Belong on the Green tour).
R.E.M. Timeline is a goldmine.
Everything but Talk About the Passion was played or demoed before the release of Chronic Town.
Harborcoat (played live prior to release of Murmur)
7 Chinese Bros (played live prior to release of Murmur)
Pretty Persuasion (demoed during Murmur sessions)
Rockville (demoed prior to Chronic Town)
Fables of the Reconstruction
Lifes Rich Pageant
Hyena (played live prior to release of Fables)
I Believe (demoed during Fables sessions)
What If We Give It Away (played live prior to Chronic Town)
Just A Touch (played live prior to Chronic Town)
Finest Worksong (portions recorded for Golden Palominos prior to LRP release)