| Opposite Day |
| Oppressor |
| Opshop |
| Opt the Game Hustler |
| Optiganally Yours |
| Optik Crew |
| Optiloop |
| Optimo |
| Optimystic |
| Opus |
| Opus 3 Jazz Trio |
| Opus III |
| Opus Pro |
| Opvs |
| Opwekking |
| Opwekking Crew |
| OQuadro |
| Oques Grasses |
| Oquinto |
| OR |
| Or |
| Or-N-More |
| Ora |
| Oracle |
| Oral Majority |
| Oran "Hot Lips" Page & His Band |
| Oran "Juice" Jones |
| Oran Thaddeus Page |
| Orange |
| Orange 9mm |
| Orange Blue |
| Orange Cake Mix |
| Orange Clubbers |
| Orange Factory |
| Orange Goblin |
| Orange Juice |
| Orange Kellin |
| Orange Range |
| Orange Sherbet |
| Oranger |
| Oranj Symphonette |
| Orba Squara |
| Orbert Davis |
| Orbison, R~Melson |
| Orbit |
| Orbital |
| Orbiuxx |
| Orch, Frank DeVol |
| Orchester Ambros Seelos |
| Orchester Claudius Alzner |
| Orchester der Vereinigten Bühnen Wien |
| Orchester der Wiener Staatsoper |
| Orchester Etienne Cap |
| Orchester Franz'l. |
| Orchester Jean-Paul Genre |
| Orchester und Chor Eric Frantzen |
| Orchestra |
| Orchestra Alfred Newman |
| Orchestra Baobab |
| Orchestra Copacabana |
| Orchestra Del Sole |
| Orchestra del Teatro Comunale di Bologna |
| Orchestra dellAccademia Nazionale di Santa Cecilia |
| Orchestra di Roma |
| Orchestra Diretta Da Bruno Nicolai |
| Orchestra E.I.A.R. |
| Orchestra Golden Nightingale |
| Orchestra Guido & Maurizio De Angelis |
| Orchestra Harlow |
| Orchestra I Cherubini |
| Orchestra Indianapolis |
| Orchestra Les Humphries |
| Orchestra Manhattan |
| Orchestra Morphine |
| Orchestra of Clare College, Cambridge |
| Orchestra Of Eternity |
| Orchestra of Mary Poppins |
| Orchestra of Opera North |
| Orchestra of St. John's |
| Orchestra of St. Luke's |
