I'm working on this prelude and there is this turn in measure 16 which in my (Henle) edition has a double-sharp accidental in parentheses printed below it (see attached image). I'm unsure how this is supposed to be played:
First of all does it apply to the A# or to the G?
Since the double sharp is below the turn symbol I guess it applies to the lower auxiliary note.
So if it applies to the A#, and I read the double-shap correctly, the lower auxiliary note would be A-natural (G raised by two half notes) that could mean the sequence should be A#-B-A#-A-A#.
If it applies to the G, I wouldn't think the double sharp applies to the upper note which is already raised once to A# and would become B making the sequence B-G-F#-G. Which seems really strange. So I think it must apply to the A#.
It would be great if someone who knows this a little better could confirm this or help me out with the correct interpretation of this sequence.
Thanks a lot!
Lars