Philip Glass, R.E.M., Regrets,

Classical composers never did that. Basically everything that Bach, Mozart, Beethoven through the romantics was fair game. What they did was something in the past (akin to film composer's now. I doubt they do much retrospective self-examining).

As a 20th C. phenomenon, artists are conscious of their own legacy. I don't think Mozart was embarrassed by Symphony No. 1. This self-consciousness is probably a result of recordings. However, I just finished Swafford's Ives biography and he continued to embrace most everything he composed (the 114 songs are a mixed bag of quality), but tinkered with almost everything till the end of his life (even way past the point where he knew what he was doing). Of course Stravinsky did the same thing but that was merely for publishing purposes (e.g. change a "flat" to a sharp in a different key"....).

Historically though, I think 19th C. composers only did revisions if they had to for some reason (Wagner making a Paris version of Tannhauser, Verdi making a Paris version of Don Carlos for the premiere, then drasticlaly shortening the opera from 5 Acts to 4 and getting rid of the mandatory Paris ballet music, etc.)

Philip Glass disavows all his "student" pieces (pre-minimalist period) which is most everything he composed before the age of 30. Had Mozart done the same he would have very little music of a "mature" voice. Same for Schubert who died at 33. We've been talking about this recently because we have all these Glass student scores here and want to record them for curiosity's sake, although I'm not sure we will be able to even if we distinguish them as disavowed. My feeling is that someday someone will find them and they will be recorded leaving the only option right now of burning them.

Composer Jennifer Higdon said recently in an interview that she is constantly embarrassed by old pieces, even popular ones, and wishes them out of circulation. My theory on all this, is that it's part of the artistic condition. Artists (usually) create in order to share something about the human experience with others. Sharing something personal usually implies exposing yourself, being vulnerable. It's no wonder that there is a constant desire for them to want to either disavow or re-examine/re-work pieces. Almost every composer I have heard of, from Korngold/Glass/Adams/Ives/Stravinsky has done this openly. Glass doesn't go back to fix old pieces, rather he often re-works musical ideas he likes over into new pieces for which he is often criticized. All this adds up to the imperfection of human beings and their unrealistic desire to do better the next time.