Artists – O
- O'Day, Anita (vocals)
- O'Hara, Kelli (mezzo-soprano)
- O'Higgins, Dave (saxophone)
- Oatts, Dick (saxophone)
- Obraztsova, Elena (mezzo-soprano)
- Ogdon, John (piano)
- Ogerman, Claus (conductor)
- Oh, Linda (double bass)
- Oh, Linda May Han (double bass)
- Oistrakh, David (violin)
- Oistrakh, Igor (violin)
- Oke, Alan (tenor)
- Oki, Itaru (trumpet)
- Olatuja, Michael (bass guitar)
- Olbertz, Walter (piano)
- Oliver, Joe 'King' (trumpet)
- Ollu, Franck (conductor)
- Olstad, Tom (drums)
- Omar (vocals)
- Onyx Brass (brass ensemble)
- Opus 5 (group)
- ORA (choir)
- Orbelian, Constantine (conductor)
- Orbit Folks (miscellaneous ensemble)
- Orchestra del Teatro Comunale di Bologna (orchestra)
- Orchestra della Svizzera Italiana (orchestra)
- Orchestra Of St. Luke's (orchestra)
- Orchestre de Chambre Jean-Francois Paillard (orchestra)
- Orchestre Métropolitain (orchestra)
- Orchestre National de la Radiodiffusion Française (orchestra)
- Orchestre Royal de Chambre de Wallonie (orchestra)
- Orchestre Victor Hugo (orchestra)
- Orfeon Donostiarra (choir)
- Ormandy, Eugene (conductor)
- Orpheus Chamber Orchestra (orchestra)
- Orquestra Simfònica de Barcelona I Nacional de Catalunya (orchestra)
- Ory, Kid (trombone and bandleader)
- Osby, Greg (saxophone)
- Oslo Philharmonic Orchestra (orchestra)
- OTOOTO (group)
- Otter, Anne Sofie von (mezzo-soprano)
- Ousset, Cécile (piano)
- Out Of/Into (group)
- Overwater, Tony (double bass)
- Owens, Jimmy (trumpet)
- Owens, Eric (baritone)
- Ozone, Makoto (piano)
