A-sharp minor
A-sharp minor has the enharmonic equivalent of B-flat minor. This is often used in most musical compositions instead of A-sharp minor, because A-sharp minor is not a useful key for compositions and is one of the least used minor keys in music. However, there were some composers in the past that have composed music in this key. Christian Heinrich Rinck wrote his Prelude No. 16 from Op. 15 in A-sharp minor.