| M Squared | | Australia |
| M&M Music | | |
| M+M Music | | United States |
| M-Outputs | | Germany |
| M-squared | | |
| M.L.Music (= Missing Link Music) | | United States |
| M.P.H. | | Netherlands |
| M.T.L. | | United States |
| M.T.T. Records | | Netherlands |
| M4TR Productions | | |
| Mad Tapes & Records | | Belgium |
| Madam Poo | | Japan |
| Magenta Mirror | | |
| Maggioli Editore | | |
| MAHCAS | | United States |
| Mahlow Productions | | |
| Main Vein Records | | |
| Making of plus show | | |
| Maldoror Tapes | | |
| Malok | | |
| MAM Music Network | | Belgium |
| MAM-Aufnahme, Ffm | | Germany |
| Man At The Off Licence | | United Kingdom |
| Man's Hate Product | | |
| mangia troppo music | | |
| MAP Tapes | | United Kingdom |
| Marginal Distribution | | |
| Markus Schwil | | |
| Marquis Tapes | | Italy |
| Mars Multimedia | | |
| Mars Multimedia / Avant Garde Films | | |
| Martin Hall | | Denmark |
| Martyrwell Music Ltd | | |
| Mary Dorothy Vertlag | | |
| Marzidovshek Minimal Laboratorium | | Slovenia |
| Masking Tapes | | Australia |
| Massimo Toniutti Editore | | |
| Master Bedroom Music | | |
| Materia Sonori | | |
| Maya Music Group | | Canada |
| Maybe Mental | | United States |
| MC-Tapes | | Germany |
| McRae Music | | United States |
| Me Tapes | | |
| Mea Culpa Records | | |
| Mechanic Casettes | | |
| Mechanical Orchestration Music | | Belgium |
| Mectpyo Sounds | | Italy |
| Media Luna | | |
| Media-Space | 1981-86 | Australia |
| Medicinal Tapes | | France |
| Medusa Evident | | United Kingdom |
| MegaMagoMusic | | Italy |
| Melodramatic Records | | Germany |
| Membrum Debile | | |
| Memphis Productions | | |
| Mensanjero Records | | Spain |
| Mental Cassettes | | Netherlands |
| Mental Decay | | |
| Mental Hygiene Cassettes | | United States |
| Mental Screen | | Japan |
| Messenger Music | | |
| Metalanguage | | |
| Metamkine | | France |
| MetationMedia | | |
| Metaware | | Germany |
| Methane Music | | |
| Methylunna Music | | United States |
| Mex | | United Kingdom |
| MHG Cassettes | | United States |
| MHN/SSP Production | | |
| Mi-Mort | | United Kingdom |
| Micrart | | Belgium |
| microDot Records | | South Africa |
| Midas Music | | Netherlands |
| Midas Tapes | | Netherlands |
| Midnight Music | | |
| Miezi Platten | | Germany |
| MiG Records | | United States |
| Migraine Music | | United States |
| Mikail Graham / Tom Reddock | | United States |
| Milchwerk-Tapes | | Germany |
| Milenoise Cassettes | | |
| Miles Long Productions | | |
| Mind And Media | | Denmark |
| Mindscan | | |
| Mindscan Tapes | | United Kingdom |
| Minerva Editions | | United States |
| Ministry of Culture | | United States |
| Ministry Of Power | | |
| Ministry Of Ultramarine Theatres | | |
| Minor 2nd Music | | |
| Minóy Cassetteworks | | |
| Minus Habens | | |
| Minus Habens Records | | Italy |
| Minus Habens Tapes | | Italy |
| Miracle and Music Unlimited | | United States |
| Mirage Tapes | | United Kingdom |
| Mirrordot | | United Kingdom |
| Mirth And Merriment Productions | | |
