A# 5/D#
The A# 5 chord consists of the A# (Perfect unison) and F (Perfect fifth) notes, with D# as the bass note.

How to play the A# 5/D# chord
- Play D# as the lowest bass note in the left hand
- Find A# (Root) on the piano keyboard
- Add F (Perfect fifth) — 7 semitones above A#
- Press all 3 notes simultaneously to sound the A# 5/D# chord