Bb 7/C
The Bb 7 chord consists of the Bb (Perfect unison), D (Major third), F (Perfect fifth) and Ab (Minor seventh) notes, with C as the bass note.

How to play the Bb 7/C chord
- Play C as the lowest bass note in the left hand
- Find Bb (Root) on the piano keyboard
- Add D (Major third) — 4 semitones above Bb
- Add F (Perfect fifth) — 7 semitones above Bb
- Add Ab (Minor seventh) — 10 semitones above Bb
- Press all 5 notes simultaneously to sound the Bb 7/C chord