| Oak Norway | | | |
| OAK Portugal | | | |
| Oaksenham | | | |
| Oaks & Fahia Spain | | | |
| Oaqk Japan | | | |
| O.A.R. United States | | | |
| Oasis United Kingdom | | | |
| Oathbringer | | | |
| The Oath | | | |
| Oatmeal Stout Canada | | | |
| Oats United States | | | |
| Frédéric D. Oberland France | | | |
| Oberon United Kingdom | | | |
| Oberon Italy | | | |
| Oberon's Parabola United States | | | |
| Oberst Norway | | | |
| Conor Oberst United States | | | |
| Obituary United States | | | |
| Obiymy Doschu Ukraine | | | |
| Object Permanence United States | | | |
| Oblique Rain Portugal | | | |
| Obliveon Canada | | | |
| Oblivio Italy | | | |
| Oblivion Protocol | | | |
| Oblivion Sun United States | | | |
| Oblomov Czech Republic | | | |
| Obrero Sweden | | | |
| Richard O'Brien United Kingdom | | | |
| O'Brother United States | | | |
| Tamara Obrovac Croatia | | | |
| Obscura Germany | | | |
| Obscura Italy | | | |
| Obscured By Clouds United States | | | |
| Obscure Sphinx Poland | | | |
| The Observatory Singapore | | | |
| Observers | | | |
| Observist Australia | | | |
| Obsidian Netherlands | | | |
| Obsidian United States | | | |
| Obsidian Kingdom Spain | | | |
| Obsidian Mantra Poland | | | |
| Obsidian Tide Israel | | | |
| Obsidian Tongue United States | | | |
| Obsidious Germany | | | |
| Obsil Italy | | | |
| Obskuria | | | |
| Obskyr Sweden | | | |
| Obsolem France | | | |
| Obstacles | | | |
| Ric Ocasek United States | | | |
| Occasional Dreams | | | |
| Occulta Veritas | | | |
| Océan France | | | |
| Ocean United States | | | |
| Ocean Norway | | | |
| Ocean Germany | | | |
| Oceana Company | | | |
| Ocean Architecture United States | | | |
| Ocean Chief Sweden | | | |
| The Ocean Doesn't Want Me South Africa | | | |
| Oceanic Portugal | | | |
| Oceanic Israel | | | |
| Oceanic Canada | | | |
| Oceanica United Kingdom | | | |
| Oceanlord Australia | | | |
| Ocean of Stars Canada | | | |
| Oceans 5 United Kingdom | | | |
| Oceans Collide France | | | |
| Ocean's Edge Greece | | | |
| Oceansize United Kingdom | | | |
| Oceans Of Night United States | | | |
| Oceans of Sadness Belgium | | | |
| Oceans Of Slumber United States | | | |
| Oceans of Time Norway | | | |
| The Ocean Germany | | | |
| Oceanus United Kingdom | | | |
| Oceill Finland | | | |
| OC Feef United States | | | |
| Och Sweden | | | |
| Ochre Australia | | | |
| Ockra Sweden | | | |
| Ocnos Spain | | | |
| Ocoai United States | | | |
| O Corbo Mudo Portugal | | | |
| Ocrilim United States | | | |
| Octafish Germany | | | |
| Octarine Sky United States | | | |
| Octavarium Sweden | | | |
| Octavio Sendero Argentina | | | |
| Octavision United States | | | |
| Octavo France | | | |
| Octillian United States | | | |
| October | | | |
| October Equus Spain | | | |
| October Falls Finland | | | |
| October Mind United States | | | |
| October Project United States | | | |
| October Tide Sweden | | | |
| Octobre | | | |
| Octohpera Brazil | | | |
| Octopie Finland | | | |
| Octoploid | | | |
| Octopus Norway | | | |
| Octopus Germany | | | |
| Octopus Chile | | | |
| Octopus United Kingdom | | | |
| The Octopus Project United States | | | |
| Octopus Ride Sweden | | | |
| Octopus Syng Finland | | | |
| La Otracina United States | | | |
| Octreocide United Kingdom | | | |
| Oddarrang Finland | | | |
| Odd Circus United States | | | |
| Odd Dimension Italy | | | |
| Odder Than 3 Italy | | | |
| Odd Fiction France | | | |
| The Odd Gallant France | | | |
| Oddisea United States | | | |
| Odd John Hawkins Puerto Rico | | | |
| Oddland Finland | | | |
| Odd Loop Denmark | | | |
| Odd Palace Denmark | | | |
| Oddplay Bulgaria | | | |
| OddsFiche Canada | | | |
| Oddtomatic Finland | | | |
| Oddzar United States | | | |
| Ode and Elegy United States | | | |
| The Odeja Italy | | | |
| Odem Arcarum Germany | | | |
| Odeon Portugal | | | |
| Odessa Italy | | | |
| Odessey & Oracle France | | | |
| Odi et Amo Italy | | | |
| Odile Germany | | | |
| Odin United Kingdom | | | |
| Odin Dragonfly United Kingdom | | | |
| Odin's Court United States | | | |
| Odissea | | | |
| Odium Canada | | | |
| Roman Odoj Poland | | | |
| Odradek Room | | | |
| Odrareg Venezuela | | | |
| Odraza Poland | | | |
| Odyssee Germany | | | |
| Odyssey United States | | | |
| Odyssey Sweden | | | |
| The Odysseys Canada | | | |
| Odyssice Netherlands | | | |
| Odz Manouk United States | | | |
| Oedipus United States | | | |
| oedipus apartment complex Spain | | | |
| Ofermod Sweden | | | |
| Offenbach | | | |
| Offenbach Canada | | | |
| Offended United Kingdom | | | |
| Offering France | | | |
| Offernat | | | |
| OFFICER! United Kingdom | | | |
| Officer Jenny United States | | | |
| Officina Meccanica | | | |
| Off Minor | | | |
| The Offspring United States | | | |
| Offworld United Kingdom | | | |
| Of Legends United States | | | |
| Of Montreal United States | | | |
| Of Noah Georgia | | | |
| Of Origins United States | | | |
| Of Petra United Kingdom | | | |
| Of Sound Mind Canada | | | |
| Rites of Spring United States | | | |
| Often the Thinker United States | | | |
| Of the I United Kingdom | | | |
| Of Virtue | | | |
| Of Wrath and Ruin United States | | | |
| Ogbert the Nerd | | | |
| OGIVES Belgium | | | |
| Oglin Sweden | | | |
| oG Musique Belgium | | | |
| O Graceful Musing’s Burden Germany | | | |
| OGRE United Kingdom | | | |
| Ogrod Wyobrazni Poland | | | |
| Naci Oğuz Turkey | | | |
| OH. United States | | | |
| Ohbliv | | | |
| OHcy-êspé Germany | | | |
| Ohead United Kingdom | | | |
| Ohgod! South Africa | | | |
| Oh Hiroshima Sweden | | | |
| Ohhms United Kingdom | | | |
| OHM United States | | | |
| Ohmme United States | | | |
| Ohmphrey | | | |
| Oh No Ono Denmark | | | |
| Oho United States | | | |
| Ohrima Netherlands | | | |
| Josefin Öhrn + The Liberation Sweden | | | |
| Oiapok France | | | |
| Oingo Boingo United States | | | |
| Oiseaux - Tempete France | | | |
| OISEAUX-TEMPÊTE France | | | |
| Oi Va Voi United Kingdom | | | |
| Eddie Ojeda United States | | | |
| Ojo En El Cielo Argentina | | | |
| Okamotonoriaki Japan | | | |
| Miles Okazaki United States | | | |
| Oketo United States | | | |
| Ok Goodnight United States | | | |
| Okko Bekker | | | |
| Oko | | | |
| Oksana Linde Venezuela | | | |
| Okta Logue Germany | | | |
| Oktober Germany | | | |
| The Oktober People United States | | | |
| Oktopus United Kingdom | | | |
| Ryo Okumoto Japan | | | |
| OK WAIT Germany | | | |
| Okyr Brazil | | | |
| O.L.D. United States | | | |
| The Old Dead Tree France | | | |
| Mike Oldfield United Kingdom | | | |
| Sally Oldfield Ireland | | | |
| Old Fruit United States | | | |
| The Old Man & the Sea Denmark | | | |
| Old Man Gloom United States | | | |
| Old Man Wizard United States | | | |
| The Old Mill Free Ensemble Italy | | | |
| Old Rock City Orchestra Italy | | | |
| Old Silver Key France | | | |
| Old Silver Key United Kingdom | | | |
| Old Time Relijun United States | | | |
| Old World Vulture Canada | | | |
| Ole Lukkoye | | | |
| Olhava Russia | | | |
| Davy O'List United Kingdom | | | |
| Oliva United States | | | |
| Olive Mess Latvia | | | |
| Oliver United Kingdom | | | |
| The Olivia Tremor Control United States | | | |
| Luca Olivieri Italy | | | |
| Olivier Lété | | | |
| Olivier Rocabois | | | |
| Olli Ahvenlahti | | | |
| Ollocs United States | | | |
| Olly Steele | | | |
| Oloferne Italy | | | |
| Olshanoe | | | |
| Lukas Olson United States | | | |
| OLTH Canada | | | |
| Oltre L'Abisso - Opera Rock Italy | | | |
| Olymp | | | |
| Olympic Czech Republic | | | |
| Anette Olzon Sweden | | | |
| Om United States | | | |
| Om Art Formation Bulgaria | | | |
| OMB Israel | | | |
| Omega Hungary | | | |
| Omega Centauri United Kingdom | | | |
| De Omega United States | | | |
| Omega Diatribe Hungary | | | |
| The Omega Experiment United States | | | |
| Omega Massif Germany | | | |
| Omega Point United Kingdom | | | |
| Omegavortex | | | |
| Omega Zero Italy | | | |
| omeme tenten | | | |
| Omenopus United Kingdom | | | |
| Omertah Ukraine | | | |
| Omesthesia Spain | | | |
| Omie Wise Portugal | | | |
| Omilgop 오미일곱 | | | |
| Omit (Clinton Williams) New Zealand | | | |
| Omnerod Belgium | | | |
| Omni Spain | | | |
| Omni | | | |
| Omnia Argentina | | | |
| Omnia Opera United Kingdom | | | |
| Omnibeing Belarus | | | |
| The Omnific Australia | | | |
| Omnimi United Kingdom | | | |
| Omnipotent Youth Society China | | | |
| Omnipresent United States | | | |
| OmnisighT Canada | | | |
| Omnium Gatherum Finland | | | |
| Omnivortex | | | |
| Omoide Hatoba Japan | | | |
| Omotai United States | | | |
| Tomoko Omura Japan | | | |
| Once & Future Band United States | | | |
| Once Them Edens Greece | | | |
| Once Upon A Winter Greece | | | |
| Onde_ModernCeltic France | | | |
| Ondskapt Sweden | | | |
| One Armenia | | | |
| One Desire Finland | | | |
| One-Eyed Monsters | | | |
| Oneida United States | | | |
| The Oneira Italy | | | |
| Oneironaught United States | | | |
| One Man Army and the Undead Quartet Sweden | | | |
| Onement9 United Kingdom | | | |
| One Million Holy Mothers United Kingdom | | | |
| One Morning Left Finland | | | |
| One Now Ago United States | | | |
| One Of These Days Spain | | | |
| Oneohtrix Point Never United States | | | |
| One Piece Puzzle Croatia | | | |
| One Shot France | | | |
| One Starving Day Italy | | | |
| One Step From The Edge Greece | | | |
| One Switch To Collision | | | |
| One Ticket to Travel Italy | | | |
| Onevoice United States | | | |
| One Way Ride United States | | | |
| OneWord Estonia | | | |
| Ongkara Russia | | | |
| Ongo Puerto Rico | | | |
| Onheil | | | |
| Oni Canada | | | |
| Onionfuzz Belgium | | | |
| Oniric Italy | | | |
| Oniric. Italy | | | |
| Onirik Portugal | | | |
| The Onirist France | | | |
| Only Bass And Drum Croatia | | | |
| Ryoko Ono Japan | | | |
| Onségen Ensemble Finland | | | |
| Onsetter | | | |
| Onslaught United Kingdom | | | |
| Ángel Ontalva Spain | | | |
| Ontariowolves Croatia | | | |
| On The Raw Spain | | | |
| על העץ [On the Tree] Israel | | | |
| On Thorns I Lay | | | |
| Ontofield United Kingdom | | | |
| Ontogeny United States | | | |
| Onyric Joy Spain | | | |
| Onysus Portugal | | | |
| Onyx Eyes Germany | | | |
| Onza Spain | | | |
| OOIOO Japan | | | |
| Oolong | | | |
| Oomph! | | | |
| Oöphoi Italy | | | |
| Oort France | | | |
| Oort Smog United States | | | |
| Oozing Wound United States | | | |
| Opa | | | |
| Opabinia Japan | | | |
| Opale France | | | |
| Opal in Sky | | | |
| Open Air France | | | |
| Open Eye Band Finland | | | |
| Open Hand United States | | | |
| Opening Scenery Italy | | | |
| Open Scenery Italy | | | |
| Opensight Colombia | | | |
| Opensight United Kingdom | | | |
| Openspace Poland | | | |
| OPERA United Kingdom | | | |
| Opera IX Italy | | | |
| Opera Magna | | | |
| Opera Obscura | | | |
| Opera Oscura | | | |
| Operation: Milksnatch United States | | | |
| Operation: Mindcrime United States | | | |
| Operose United Kingdom | | | |
| Opeth Sweden | | | |
| The Ophelias United States | | | |
| Ophiucus France | | | |
| Ophiura Italy | | | |
| Ophthalamia Sweden | | | |
| Opinion | | | |
| The Opium Cartel Norway | | | |
| Opposing Motion United Kingdom | | | |
| Opposite Day United States | | | |
| Opposite Earth | | | |
| The Opposite of Hate Brazil | | | |
| Opram France | | | |
| Opra Mediterranea Italy | | | |
| Opsis Italy | | | |
| Optical 8 Japan | | | |
| Optic Yellow Felt Brazil | | | |
| Optimystical Sweden | | | |
| Optimystik Visionaries United Kingdom | | | |
| Opus Yugoslavia | | | |
| Opus 3 | | | |
| Opus-5 Canada | | | |
| Opus Arise Canada | | | |
| Opus Avantra Italy | | | |
| Opusculus Canada | | | |
| Opus Däi United States | | | |
| Opus Est Sweden | | | |
| Opus of a Machine Australia | | | |
| Opus Symbiosis Finland | | | |
| Opus Tide United Kingdom | | | |
| Opus V Brazil | | | |
| O Quarto Fantasma Portugal | | | |
| Oracle Spectre | | | |
| Orakle France | | | |
| .O.rang United Kingdom | | | |
| Orange Clocks United Kingdom | | | |
| Orange Goblin United Kingdom | | | |
| Orange Peel Germany | | | |
| Orange Shading Starlight Italy | | | |
| Orange Tulip Conspiracy United States | | | |
| Ora Nombro Italy | | | |
| Oranssi Pazuzu Finland | | | |
| Oranzada Poland | | | |
| Oratrism France | | | |
| Or Best Offer | | | |
| Orbit 17 United States | | | |
| Orbital | | | |
| Orbit Culture | | | |
| Orbs United States | | | |
| The Orb United Kingdom | | | |
| Orchestral Manoeuvres in the Dark | | | |
| Orchestra Njervudarov Italy | | | |
| Orchestra Of The Upper Atmosphere United Kingdom | | | |
| Orchestra Panica Italy | | | |
| Orchestre Celesti Italy | | | |
| L' Orchestre Sympathique Canada | | | |
| Orchid United States | | | |
| Orcustus | | | |
| Orden Ogan Germany | | | |
| Order of Nine United States | | | |
| Order of Nosferat | | | |
| The Ordinaires United States | | | |
| Ordinaires,The United States | | | |
| Ordinary Brainwash Poland | | | |
| Ordo Draconis Netherlands | | | |
| Ordo Ignis Germany | | | |
| Oregon United States | | | |
| Orenda France | | | |
| Orfeu Rebelde Portugal | | | |
| Carl Orff Germany | | | |
| Martin Orford United Kingdom | | | |
| Organ: Norway | | | |
| Organic Acid United States | | | |
| Organic Is Orgasmic Russia | | | |
| Organic Noises Poland | | | |
| Organic Reaction Brazil | | | |
| Organic Toy Serbia | | | |
| Organisation Germany | | | |
| Organised Chaos Serbia | | | |
| Organissimo United States | | | |
| Organized Chaos Serbia | | | |
| Organon | | | |
| Orgiya Pravednikov Russia | | | |
| Orgiya Pravednikov/оргия Праведников | | | |
| Orgone United States | | | |
| Orianthi Australia | | | |
| Ori Barel | | | |
| Oriental Spas United States | | | |
| Oriental Sunshine | | | |
| The Orient Express | | | |
| Orient Squeezers Sweden | | | |
| Origens Brazil | | | |
| Origin United States | | | |
| Origin Pulse France | | | |
| Origins United States | | | |
| Orion France | | | |
| Orion United Kingdom | | | |
| Ørion Georgia | | | |
| Orion Dust France | | | |
| Orion's Beethoven Argentina | | | |
| Orion's Reign Greece | | | |
| Orion Tango United States | | | |
| ORISSA United States | | | |
| O.R.K. Italy | | | |
| Ork France | | | |
| O.R.K Italy | | | |
| Orkenkjott Norway | | | |
| Andrea Orlando Italy | | | |
| Michael Orlando United States | | | |
| Pawel Orlow Belarus | | | |
| The Orne | | | |
| Ornithos Italy | | | |
| Oro | | | |
| Orodruin | | | |
| Oromet | | | |
| Orotoro France | | | |
| Orphalis | | | |
| Orphan Bloom United States | | | |
| Orphaned Land Israel | | | |
| Orphan Project United States | | | |
| Orpheo Netherlands | | | |
| Orpheus United Kingdom | | | |
| Orpheus Japan | | | |
| Orpheus Blade Israel | | | |
| Orpheus Nine United States | | | |
| Orquesta Metafísica Argentina | | | |
| Orquestra Mirasol Spain | | | |
| Orquestra Plateria Spain | | | |
| Orsak:Oslo Sweden | | | |
| Orthodox Spain | | | |
| Orthotonics United States | | | |
| Orthrelm United States | | | |
| Orvalians France | | | |
| Orwell United States | | | |
| Oryad United States | | | |
| Oryzhein Canada | | | |
| Osada Vida Poland | | | |
| Osage Tribe Italy | | | |
| Osanna Italy | | | |
| Ozzy Osbourne United Kingdom | | | |
| Oscil France | | | |
| The Oscillation United Kingdom | | | |
| Oscillazioni Alchemico Kreative Italy | | | |
| Oscillotron Sweden | | | |
| OSE France | | | |
| Oshean Russia | | | |
| OSI United States | | | |
| Osiah United Kingdom | | | |
| Osi and the Jupiter | | | |
| Osibisa Ghana | | | |
| Osiris Netherlands | | | |
| Osiris Bahrain | | | |
| The Osiris Club United Kingdom | | | |
| Osiris The Rebirth United Kingdom | | | |
| Osirys France | | | |
| Osjan / ex Ossian Poland | | | |
| Oslo Tapes Italy | | | |
| Osmosis United Kingdom | | | |
| Os Mundi Germany | | | |
| Ossian / Osjan | | | |
| Ossicles Norway | | | |
| Ossi Duri Italy | | | |
| Osta Lcve Germany | | | |
| Osta Love Germany | | | |
| Ostara Czech Republic | | | |
| Ostinato United States | | | |
| Ostraca | | | |
| Ostrich Society Norway | | | |
| Ostrova Spain | | | |
| Ostura Lebanon | | | |
| Daniel O'Sullivan United Kingdom | | | |
| Osyron Canada | | | |
| Kiyomi Otaka Japan | | | |
| Ota Petrina | | | |
| Otargos France | | | |
| OT&DO Russia | | | |
| oteme Italy | | | |
| Oteme Israel | | | |
| Otep | | | |
| O! The Joy United States | | | |
| The Othello Syndrome United Kingdom | | | |
| Others by No One United States | | | |
| The Other Side of the Sky United States | | | |
| The Other Side United States | | | |
| Other View Italy | | | |
| The Otolith United States | | | |
| Otolithen United States | | | |
| Otomo Yoshihide Japan | | | |
| Oto Spooky France | | | |
| Matt Ottewill United Kingdom | | | |
| Ottone Pesante Italy | | | |
| O-U Japan | | | |
| OU China | | | |
| Oubliette | | | |
| Ougenweide Germany | | | |
| Oulu Space Jam Collective Finland | | | |
| Our 11th Hour United States | | | |
| Our Brother The Native United States | | | |
| Our Destiny United States | | | |
| Our Lady Of The Highway United States | | | |
| Our Lady Peace Canada | | | |
| Our Man In The Bronze Age United Kingdom | | | |
| Ourobiguous United States | | | |
| Our Oceans Netherlands | | | |
| Ourselves, Alone United States | | | |
| Our Solar System United States | | | |
| Our Survival Depends On Us Austria | | | |
| Chris Ousey United Kingdom | | | |
| Ous Mal Finland | | | |
| Ousstal France | | | |
| Outcast France | | | |
| Outdeth Brazil | | | |
| Outer Heaven | | | |
| Outer Limits Japan | | | |
| The Outer Space Milkmen | | | |
| The Outfield United Kingdom | | | |
| Outfit | | | |
| Out for the Count France | | | |
| OUt iNK United Kingdom | | | |
| Outlander | | | |
| Outlanders | | | |
| Outlasted Norway | | | |
| Outlier Canada | | | |
| Outofchannel Russia | | | |
| Out of Darkness United Kingdom | | | |
| Out of Focus Germany | | | |
| Out Of The Beardspace United States | | | |
| Outopsya Italy | | | |
| Outre Mesure France | | | |
| Outroduction France | | | |
| Outrun the Sunlight United States | | | |
| Outside France | | | |
| Outside In New Zealand | | | |
| Outsound Ireland | | | |
| Outstation United Kingdom | | | |
| Outworld United States | | | |
| Ouzo Bazooka Israel | | | |
| Ovalki Finland | | | |
| The Ovals Australia | | | |
| Overdrive Italy | | | |
| Overdrive Sensation | | | |
| Overdub Spain | | | |
| Overfloaters Czech Republic | | | |
| Overhead Finland | | | |
| Overkhaos Italy | | | |
| Overkill United States | | | |
| Overlife Spain | | | |
| Overload Pakistan | | | |
| Overlorde | | | |
| Overmars France | | | |
| Overmars Japan | | | |
| Over The Earth France | | | |
| Over the Ocean United States | | | |
| Overture Italy | | | |
| Overtures Italy | | | |
| Overworld Dreams United States | | | |
| Ovni El Salvador | | | |
| OM (aka Ovnimoon) Chile | | | |
| Ovo Spain | | | |
| Ovrfwrd United States | | | |
| Ov Shadows | | | |
| Ovum | | | |
| Owane Norway | | | |
| Owen Jane United States | | | |
| Tim "Ripper" Owens United States | | | |
| Owie Pockshull Croatia | | | |
| Owl United States | | | |
| Owl (Germany) Germany | | | |
| The Owl Archimedes United States | | | |
| The Owl Watches United States | | | |
| Oxbow United States | | | |
| Oxcart United States | | | |
| Ox.Eagle.Lion.Man United Kingdom | | | |
| Oxes | | | |
| Oxhole Czech Republic | | | |
| Oxhuitza Italy | | | |
| Oximora Mexico | | | |
| Oxiplegatz | | | |
| Oxomaxoma Mexico | | | |
| Oxx | | | |
| Oxygen Destroyer United States | | | |
| Oymyakon United States | | | |
| Oysterhead United States | | | |
| Oz Knozz United States | | | |
| Burak Ozmucur Turkey | | | |
| Ozone Quartet United States | | | |
| Ozric Tentacles United Kingdom | | | |
| Ozul Norway | | | |
