Strictly this is ‘back down to A’. The Scherzo of Mahler’s 1st symphony is written in A major. I turned on the car radio in the middle of the vigorous first section. I was not surprised to be hearing it up a semitone in B flat. Not what I would have chosen as my brain ‘sees’ the violins playing the wrong notes, so I can’t hear music purely for itself. When this section ends after whooping horns take over the rapid rising 5 note string theme, a single horn holds the key note of A, slows the music down and the A becomes part of the F major chord key for the slow Landler-type middle section. So the horn should have held a B flat to my altered key sense. But immediately it was an A and the music and I, in concert once more, moved into the written key of F, and stayed there. That is, till we parted company again when the Scherzo music returned….