E b5/B#
The E b5 chord consists of the E (Perfect unison), G# (Major third) and Bb (Diminished fifth) notes, with B# as the bass note.

How to play the E b5/B# chord
- Play B# as the lowest bass note in the left hand
- Find E (Root) on the piano keyboard
- Add G# (Major third) — 4 semitones above E
- Add Bb (Diminished fifth) — 6 semitones above E
- Press all 4 notes simultaneously to sound the E b5/B# chord