| 554. Obed Vazques | Horns, Spoons | 1 |
| 554. Obi Nwadije | Percussion | 1 |
| 554. Obinna Enwere | Keys | 1 |
| 554. Odeal | Vocals | 1 |
| 554. Odessa Jorgensen | Violin | 1 |
| 554. Of Montreal | Featured Artist | 1 |
| 554. Ogueji Kenneth Uchenna | Guitar | 1 |
| 554. Oh Pep! | Featured Artist | 1 |
| 554. Ohmme | Featured Artist | 1 |
| 554. Okkervil River | Featured Artist | 1 |
| 554. Oklou | Guitar, Marimba, Piano, Recorder, Vocals | 1 |
| 554. Olabiyi Julius | Keys | 1 |
| 554. Old Crow Medicine Show | Featured Artist | 1 |
| 554. Ole Kirkeng | Bass | 1 |
| 554. Olena Tsybulska | Drums, Vocals | 1 |
| 554. Olga I. González | Background Vocals, Shaker, Tambourine | 1 |
| 554. Oli Harris | Cello | 1 |
| 554. Oli Jefferson | Drums | 1 |
| 554. Oli Langford | Violin | 1 |
| 554. Olive Hannah | Drums | 1 |
| 554. Oliver "Tuku" Mtukudzi | Featured Artist | 1 |
| 554. Oliver Bates Craven | Electric Guitar, Fiddle, Vocals | 1 |
| 554. Oliver Pinnell | Guitar | 1 |
| 554. Oliver Tuttle | Trombone | 1 |
| 554. Olivia 'Livi Lovez' Williams | Vocals | 1 |