| Abbreviation | Definition |
|---|---|
| O | Orchestra |
| O | Overs |
| O3O | o3o |
| OACB | Oshkosh Area Community Band |
| OAE | Orchestra of the Age of Enlightenment |
| OAMC | Oregon Adventist Mens Chorus |
| OASL | Orchestre d'Accordéons de Saint-Louis |
| OASO | OBERLIN ARTS AND SCIENCES ORCHESTRA |
| OAUE | Online Accuracy Updated Ensemble |
| OB | Only Bass |
| OBB | Oswald Brothers Band |
| OBCF | Octave Band Center Frequency |
| OBD | Old Blues Dude |
| OBF | Old Band Friends |
| OBG | Oldie But Goodie |
| OBMS | Out of Band Management Settings |
| OBMT | Off Broadway Musical Theatre |
| OBQ | Oshkosh Brass Quintet, Oshkosh, Wisconsin |
| OBQ | Overture for Brass Quintet |
| OBR | Ouija Board Reunion |