| o01 | Typhoon OS Voice Data |
| obw | Superior Drummer Sound File |
| ocdf | OneClickDigital Audio Book |
| odd | Coby Voice Recorder Data |
| ofg | OptimFROG Dualstream Audio |
| ofr | OptimFROG Lossless Audio |
| oga | Ogg Vorbis Compressed Audio |
| ogg | Ogg Vorbis Compressed Audio |
| ogx | Ogg Vorbis Compressed Audio |
| okt | Oktalyzer Music Module |
| olv | OnLive! Traveler Sound |
| oma | Sony ATRAC3 Compressed Audio |
| omg | Sony OpenMG Audio |
| omg | Sony ATRAC3 Compressed Audio |
| oml | OtsAV Media Library |
| omx | OtsAV Media Library Information |
| opm | FM Operator Type-M Voice Data |
| opu | Opus Audio File |
| opus | Opus Audio File |
| orc | Voyetra Digital Orchestrator Pro Song |
| orc | TRS-80 Orchestra-90 Audio Data |
| osp | Orion Sampler Program |
| ots | OtsAV Album |
| p | AKAI S900 Program |
| p3k | Kurzweil PC3K8 Audio Data |
| p40 | The Player 4.0 Music Module |
| p4x | The Player 4.x Music |
| p50 | The Player 5.0a Module |
| p5b | NI Pro-53 Bank |
| p60 | The Player 6.0 Music Module |
