If there are boundaries of musical propriety Schumann transcends them all in Waldszenen. Fixed tempo evaporates into fantasy, not programmatic fantasy but tonal fantasy. Every deviation is occasioned by a transformation dictated by the sound. But the player must hear it in order to make it happen.
That is the hard part. We tend to take comfort in regular beats and knowable harmonies. What happens when we let go of these preconceptions is that fast is free to go faster, slow slower than we would have thought possible.
I was fortunate to study piano with Hans Neumann who used to characterize some music as impossible to play while sober. Schumann's late work is of this category.
