No. It would be F#X or Bb bb. (F sharp double-sharp or B flat double-flat.)
The equivalent of an f sharp is a G flat.
A flat
It's because that note is the only one two half-steps away from another flat/sharp note in both directions.
I am guessing so... I've seen something like a key signature having a B-flat, and somewhere in the piece there is a flat in front of a B, so it would be a B-double-flat. If double flats are allowed,then it would be C,B-sharp;C-sharp,D-flat;D, E-double-flat; D-sharp, E-flat; E, F-flat;F,G-double-flat;F-sharp,G-flat;G,A-double-flat;G-sharp,A-flat;A,B-double-flat;and B,C-double-flat.
It's called enharmonic spelling. An example is C-sharp and D-flat.
The enharmonic equivalent to A-flat is G-sharp; The enharmonic equivalent to G-flat is F-sharp.
The equivalent of an f sharp is a G flat.
Being that it's a whole-step away from another sharp or flat note in both directions, there is no possible double-sharp/flat spelling for it.
A flat
It's because that note is the only one two half-steps away from another flat/sharp note in both directions.
G sharp (enharmonic A flat).
I am guessing so... I've seen something like a key signature having a B-flat, and somewhere in the piece there is a flat in front of a B, so it would be a B-double-flat. If double flats are allowed,then it would be C,B-sharp;C-sharp,D-flat;D, E-double-flat; D-sharp, E-flat; E, F-flat;F,G-double-flat;F-sharp,G-flat;G,A-double-flat;G-sharp,A-flat;A,B-double-flat;and B,C-double-flat.
G double sharp is a very clumsy way of saying (enharmonically) "A natural".
A flat. Because this note is between G and A, you can go up from G (make it a sharp) or down from A.
G sharp (enharmonic A flat).
F sharp is the enharmonic.
Enharmonic