Gb add13/Bb
The Gb add13 chord consists of the Gb (Perfect unison), Bb (Major third), Db (Perfect fifth) and Eb (Major thirteenth) notes, with Bb as the bass note.

How to play the Gb add13/Bb chord
- Play Bb as the lowest bass note in the left hand
- Find Gb (Root) on the piano keyboard
- Add Bb (Major third) — 4 semitones above Gb
- Add Db (Perfect fifth) — 7 semitones above Gb
- Add Eb (Major thirteenth) — 21 semitones above Gb
- Press all 5 notes simultaneously to sound the Gb add13/Bb chord