A question that seems to have puzzled some composers of symphonies is the following: should the slow movement be the second movement, preceding the Scherzo, or should it be the other way around?
Beethoven changed his mind only in his final (9th) symphony, putting the Scherzo in the second movement. So did Bruckner in his last two symphonies (8th and 9th). Mahler was ambivalent concerning this issue in his own 6th symphony, of which two versions exist where the Scherzo is placed either 2nd or 3rd.
Rachmaninov had an ingenious idea in his 3rd symphony: he "sandwiched" the Scherzo within the slow (second) movement, creating a most symmetric structure of the form ABA (A=slow, B=fast). Who says a great pianist cannot be simultaneously a very inventive master of symphonic form?
