Index - O
| oboe | Instrument |
| ocarina | Instrument |
| Octave | Pitch |
| Off | Midi |
| On | Midi |
| openCuica | Drum |
| openHiConga | Drum |
| openHiHat | Drum |
| openTriangle | Drum |
| orchestraHit | Instrument |
| orchestralHarp | Instrument |
| overdrivenGuitar | Instrument |
live-sequencer-0.0.5.1: Live coding of MIDI music