Top 99 Publishers
- Oxford University Press Digital (3311)
- Oxford University Press (2919)
- Open Cloud (21667)
- Olt Music (1084)
- Opus 3 Music/Trio Music Publishing (339)
- O'Meara Music (1401)
- Official Broadway Arrangements (29)
- Olive W Chen (56)
- Opus III Wind Orchestra Publications (2319)
- Overture & Storybook Musical Arrangements (43)
- ORLAN CHARLES MARCHIORI PRADO (83)
- Oni Rodila (13)
- Omni Music Publishing (33)
- Ocelot Music (35)
- Oliver Gies (member of Maybebop) (21)
- Onaipo Arrangement (38)
- OlivePress Music (78)
- Oak Publications (30)
- Ossian Publications (37)
- Opus 125 Publishing (59)
- Ognyan Petrov (32)
- Oscar Eduardo Pena (30)
- Odd Shoe Music (138)
- Ovidio De Ferrari (18)
- Omar Felipe (18)
- Ollie Kaiper-Leach (25)
- Olesia Skopiuk (12)
- Olga Leonard (50)
- oySongs (306)
- Osgoode Music (10)
- Ondrej Pavlicek (11)
- Overda Page Stonerock (17)
- On Note Editions (17)
- Off-Key 101 (48)
- Oleksandra Spasichenko (22)
- Othello Music Publishing (16)
- Oleksii Bazhenov (63)
- OCP (255)
- Oertel Musikverlag (51)
- Omnibus Press (60)
- OR-TAV Music Publications (42)
- Ortus Musikverlag (28)
- Ondine Press (78)
- Oscar Tagle (15)
- OTBM (58)
- Oliver Koenig (103)
- Ogilvy Music (12)
- Oh Pray Productions, LLC (12)
- Obijiaku C.C (29)
- Ocean6pm Music Publishing (10)