There are two types of composers: those that revise, and those that do not. I am not talking about making corrections—a wrong note here or there—but actually making major changes: ripping apart and re-constructing sections, adding new notes, changing dynamics and articulations, and so on. There are many great composers who edited older works—Sibelius, Schoenberg, Stravinsky, Boulez and Ives, to name a few—but others simply do not like to go back or feel they do not need to, or only make changes when there are very minor details that need fixing, like Christopher Rouse and Poul Ruders. This is not a black and white issue of course. One composer's revision is another composer's minor tweak. Some revisions are musical, others are technical. I have been thinking about this a lot lately because I recently revised a work I wrote thirteen years ago, a forty-minute piece for piano trio called Sun Trio that will finally be premiered in Los Angeles by an enterprising new trio. It was almost surreal, revising something I wrote so long ago. It felt close to my heart, but distant at the same time. As the piece and I became intimately reacquainted, it felt good—like reconnecting with an old friend, or a son who has moved away (or in this case, Sun).
This brings up another interesting issue: that of altering works written long ago. Is it worth it? In this case, I made a few errors that I now realize can be fixed without harming my original intention; for example, I wrote a few notes as harmonics that work much better as regular pitches. Back then, I was even more obsessed with dynamic shading than I am now, but in a few spots, I think I went way over the top. I also increased a few tempos, easily shaving off a good minute or two from the entire work. By changing these details, the piece will still sound the same, but will be much more playable. None of my revisions were huge, but everything just feels better now.
A final issue I have been obsessed with lately is the concept of having a separate editor. By default, composers are their own editors. I think this, more than anything, is the most difficult role to teach composition students: the importance of being self-critical, without pandering to trends and the tastes of others.
In some disciplines such as film, collaboration is normal. Classical composers—unless they work in the film industry or only write operas or musicals—almost never have an outsider edit their music, or even suggest edits. Can you imagine? Long, boring swaths of music in pieces by certain long-winded composers (I won't mention names) would be cut. What a thrill that would be, and imagine the millions of hours saved!
As Ruders once said in an interview, perhaps experience is what makes the difference, but if there's a good reason, revisions are OK. In the end, it depends on the composer, the work and when it was written, but most importantly, composers should always feel free to make changes if they will make a piece better.