Obrecht, Jacob
Ochs, Siegfried
Ockeghem, Johannes
Odo van Cluny
Oestvolskaja, Galina
Offenbach, Jacques
Ogdon, John (Andrew Howard)
Ohana, Maurice
Onslow, (André) Georges (Louis)
Orff, Carl
Orthel, Léon
Ortiz, Diego
Osiander, Lukas
Othmayr, Caspar
Otterloo, (Jan) Willem van