Ab maj7/C
The Ab maj7 chord consists of the Ab (Perfect unison), C (Major third), Eb (Perfect fifth) and G (Major seventh) notes, with C as the bass note.

How to play the Ab maj7/C chord
- Play C as the lowest bass note in the left hand
- Find Ab (Root) on the piano keyboard
- Add C (Major third) — 4 semitones above Ab
- Add Eb (Perfect fifth) — 7 semitones above Ab
- Add G (Major seventh) — 11 semitones above Ab
- Press all 5 notes simultaneously to sound the Ab maj7/C chord