The Note A#/Bb

A#/Bb sits one semitone above A. As Bb it is one of the most important keys in jazz, brass, and wind music — trumpets and clarinets are typically Bb instruments. Bb major sounds warm and rounded, the horn-section key, while Bb minor is heavy and brooding — the key of Chopin's Funeral March. Its reference octave pitch is 466.16 Hz (MIDI note 70). The major triad on A# is A#/Bb Major (Bb – D – F), and the minor triad is A#/Bb Minor (Bb – Db – F).