A# minor is the relative minor key to C# major. Both have 7 sharps in the key signature.
Here are the A# harmonic minor scales:
And the A# melodic minor scales:
A# sharp minor seems complicated on the surface, but it works in the same way as A minor, with every note of the scale raised by a semitone. G# in the scale of A minor becomes G## in A# minor, and in the melodic ascending scale, F# becomes F##.
There is virtually no music written in the key of A# minor (since the enharmonic equivalent key of Bb minor is much simpler).
However, Christian Rinck (1770-1846) included an Exercise in A# minor in his Organ tutor book (op.55 no.1). This is how it begins (the lowest stave is played on the organ’s foot pedals). (The D## is a chromatic note and not part of the key).
A Flat Minor
Ab minor is the relative minor to Cb major. Both keys use seven flats in the key signature.
Here are the Ab harmonic minor scales:
And the Ab melodic minor scales:
Ab minor works like A minor, but with every step of the scale lowered by a semitone.
Like A# minor, the key of Ab minor is hardly ever used, but it does exist; for example in Isaac Albéniz’s “Evocación” from his Iberia Suite.
You might also encounter it as a modulation key within a piece of music that begins in a different key.