O-P-S Records

O-Rama

O.L.

Oak

Oak Records

Oasis

Oausa

Object Music

Oblique

Obscure Alternatives

Obscure World

Obvious Moose

OC5

Ocean

Ocora

ODA

Ode

Ode Records

Odeon

Odeon / Alhambra

Odin

Odyssey

Odyssey Music Network

Off The Hook

Offence Records

Office de Radiodiffusion-Télévision Française (ORTF)

Official

Official Bootlegger! K.G.L.W.

Official Mickey Mouse Club

Ogun

Oh Boy Records

Ohr

OJC

Okra

Old Friends

Old Homestead

Old Timey Records

Old Town

Olde World

Oldie Blues

Olfactory

Olive Tree

Olivia

Olivia Records

Olle

Olle I Skratthult Project

Olmec

Olufsen

Olydor

Olympia

Olympic

Olympic Records

Olympic Records (4)

Olympico

Omari

Omega

Omega Records (13)

Omni Arts

Omni Sound

Omnisound

Omnivore

Omnivore Recordings

Omplatten

OMV / Preisser

On The Air

On The Spot

On-U

On-U Sound

Onari

Ondine

One Little Independent Records

One Little Indian

One Little Indian / One Little Independent

One Man Band

One Nation One Mind Records

One Star Project

One-Up

Onslo Record

ONYX

Onyx Records

Opal

Open

Open Air

Open Sky

Optimism

Optimism Incorporated

Opus

Opus 3

Opus 3 (2)

Opus One

OR

Orange Tree Press, Inc. Records

Oresound

Orfeo

Orfeon

ORG

ORG Music

Organic Music

Oriel

Origin

Original

Original Blues Classics

Original Cast

Original Cast Records

Original Jazz Classics

Original Music

Original Recordings Group

Original Records Group

Original Recoreds Group

Original Rock Classics

Original San Francisco Record Company

Original Sound

Orinda

Orinda Records

Orion

Orion Master Recordings

ORO

Orpheus

Orphic Egg

Orphic Egg / London Records

Ortho Jazz

Oryx

Oryx Romantic

Oscar Records

OSOD

Ossum Possum

Our First Record

Our Gang Entertainment / Mirus Music

Out

Out Loud

Out Loud Records

Out Of Darkness Records

Out Of Tune

Out Of Your Element

Out-Sider

Outside Music

Outsider

Outstanding

Outstanding Records

Ovation

Ovation Records

Oversea

Overseas

Overseas Records

Overtone

Overweight Rat

Owl

Oxford

OYOY

Oyster