California, IIRC, Villella responded to your question in one of his pre-performance talks when someone in his audience asked it that MCB calls the ballet
Ballet Imperial instead of
Tschaikovsky Piano Concerto No. 2 because
Ballet Imperial is an easier name to sell. (I've been looking all over BA! without being able to find any of my accounts of these talks.)
If you have a look at the video in pherank's first post (while you can, it may not remain), I think you'll see that second-movement pas deux begin about 20 minutes into the video, where the boy stands downstage, back to us, and she enters upstage and comes down to him between columns of corps. I never saw the earlier versions of the choreography or the costumes and find this version wholly satisfying, but then, as I've just said, I don't really know what I'm missing.
Edited to answer California explicitly, what we see here is what MCB has been doing - or most of it, acknowledging the gaps in the video - in the several years since they mounted this ballet, the 1973 version, as regards both choreography and costumes.
In the case of
Apollo and to a lesser extent,
Emeralds, for example, I'm less happy with the later version than with the earlier, which in the case of
Apollo Suzanne Farrell prefers to present with her troupe. In the case of
Valse Fantaisie, I like the middle version (1953, danced recently by MCB) better than the last, 1967 setting, but these are really different ballets to the same music.
Even so, I hesitate to generalize about Balanchine's revisions; I gather the first version of
La Source was too strenuous and it was made successful only by insertion of some corps material, for example. And in tinkering with his distillation of
Swan Lake, he eliminated the synchronized little dance for the four cygnets which has always seemed to me mechanical when I see it in traditional productions. The two minutes pas d'action fight of the Prodigal's servants, shown recently by TSFB and included in the MCB version of
Prodigal Son, looks weak to me; and the restored divertissment in
La Sonnambula, staged by Frederic Franklin in Cincinnati a few years ago looked like weak choreography to weak music.
Edited by Jack Reed, 28 November 2012 - 08:46 AM.