I have been in NYC and SF, so missed a lot of postings. Doug called me about Midsummer music and orchestrations. The full orchestra is used to play the entire ballet, of course, but Sinfonia IX in C Major is the "Divertissement" coming just after the Wedding March. There is an 8 bar segue (composed by R. Irving, I believe) into the Sinfonia Nol. 9. The second movement is used, but only the first and last sections. It was choreographed at first, but Balanchine took it out. Too long, he said. The 3rd movt., is not used anymore. After the Sinfonia, which just ends, the "Son and Stranger" opus begins, the first part of which has the Divert couples exiting, and the Wedding March couples entering, with the soloists (lovers, etc.) At the conclusion of this, the incidental music (overture) returns, with Oberon and Titania, scene changes to forest, and ends with Puck sweeping the stage. I do think the ballet is masterfully conceived, and I never tire of watching (or playing it). Mr. B. did make the piano arrangement from the score for Sinfonia No. 9, (He also made the piano reduction of Mozart's Divertimento No. 15).
Have also seen Ashton's 'Dream' which is most beautiful (if shorter). Thanks, Doug for telling me about this post, and telephoning for information.