E dim/A#
The E dim chord consists of the E (Perfect unison), G (Minor third) and A# (Diminished fifth) notes, with A# as the bass note.

How to play the E dim/A# chord
- Play A# as the lowest bass note in the left hand
- Find E (Root) on the piano keyboard
- Add G (Minor third) — 3 semitones above E
- Add A# (Diminished fifth) — 6 semitones above E
- Press all 4 notes simultaneously to sound the E dim/A# chord