| Operation Ivy |
10 |
| Operator Please |
14 |
| Opeth |
40 |
| Ophelie Winter |
8 |
| Ophthalamia |
14 |
| Opiate For The Masses |
16 |
| Opium Project |
15 |
| Oppera |
9 |
| Oppnox |
3 |
| Opposition |
13 |
| Opposition Of One |
4 |
| Oppressor |
7 |
| Opshop |
9 |
| Optiganally Yours |
5 |
| Optimus Prime |
13 |
| Optimus Rhyme |
5 |
| Optimystica Orchestra |
8 |
| Opus |
7 |
| Opus III |
13 |
| Opus Podunk |
5 |
| Oracle |
7 |
| Orange |
6 |
| Orange 9mm |
7 |
| Orange Blue |
8 |
| Orange Caramel |
11 |
| Orange Goblin |
16 |
| Orange Juice |
10 |
| Orange Sky |
6 |
| Oranger |
3 |
| Oratory |
14 |
| Orba Squara |
7 |
| Orbision Roy |
8 |
| Orbit |
8 |
| Orbita Wiru |
3 |
| Orchestral Manoeuvres In The Dark |
21 |
| Orchid |
24 |
| Orcivus |
5 |
| Ordain |
9 |
| Ordalium |
4 |
| Orden Ogan |
23 |
| Order From Chaos |
6 |
| Ordinary Boys |
9 |
| Ordo Draconis |
5 |
| Ordo Equilibrio |
3 |
| Ordo Rosarius Equilibrio |
15 |
| Ore Ska Band |
9 |
| Oren Lavie |
3 |
| Orenda Fink |
13 |
| Orfeh |
6 |
| Orff Carl |
3 |
| Organic Infest |
5 |
| Orgy |
18 |
| Orianthi |
19 |
| Origa (Ольга Яковлева) |
6 |
| Origami |
10 |
| Origin |
19 |
| Original 3 |
4 |
| Original Broadway Cast |
9 |
| Orikasa Ai |
14 |
| Orion |
7 |
| Orion Riders |
8 |
| Orishas |
6 |
| Orkest Klein |
7 |
| Orkrist |
4 |
| Orla Gartland |
3 |
| Orlando |
11 |
| Orleans |
11 |
| Ornatos Violeta |
6 |
| Ornella Vanoni |
18 |
| Orphan Lily |
5 |
| Orphanage |
8 |
| Orphaned Land |
26 |
| Orpheus and Eurydice |
13 |
| Orson |
15 |
| Orthodox Celts |
6 |
| Os Mutantes |
18 |
| Os Paralamas Do Sucesso |
31 |
| Osb |
7 |
| Osborne Joan |
10 |
| Osborne Ozzy |
7 |
| Oscar Benton |
6 |
| Oscar Brand |
5 |
| Oscar Hammerstein |
4 |
| Oscar Rose |
3 |
| Osiris |
20 |
| Osmonds |
3 |
| Ossastorium |
6 |
| Ossian |
12 |
| Osullivan Gilbert |
3 |
| Osvaldo Murti |
9 |
| Ot Vinta |
9 |
| Otan Vargas |
6 |
| Otava MC |
5 |
| Otep |
47 |
| Other Lives |
5 |
| Otherwise |
12 |
| Otierre |
3 |
| Otis Redding |
7 |
| Otis Taylor |
3 |
| Otsuka Ai |
3 |