Guitar chords in the key of A# or Bb:
Chord Bbmaj7 (5th fret) notes: Bb, D, F and A. You must leave out the 6th and 5th strings.
Bb(A#) major 7th guitar chord's alternative names: BbM7, Bbmaj7.
1(A#/Bb), 3(D), 5(F), 7(A).