| C.I.A. Records | | |
| C.T.O.A.N. | | United Kingdom |
| Cabarte | | United Kingdom |
| Cabarte Mag | | |
| Cabvolt Publications Ltd. | 1978 | United Kingdom |
| Caedmon | | United States |
| Cafardage | | |
| Calypso Now | | Switzerland |
| Camaraderie Music | | United States |
| Camera Obscura | | Belgium |
| Can-Can | | Germany |
| Canada Council Media Art | | |
| Canoe | | France |
| Cantrecordings | | Canada |
| Caravan Of Dreams Productions | | |
| Carmine Tapes | | |
| Carnival Tapes | | United Kingdom |
| Carnivor Tapes | | Germany |
| Casetiau Neon | | |
| Cassette Curriculum | | United States |
| Cassette Documents | | United States |
| Cassette Factory | | Belgium |
| Cassette Gazette | | Belgium |
| Cassette King | | United Kingdom |
| Cassette Mythos | | United States |
| Cassettencombinat | | Germany |
| Cassettes Proceso Uvegraf | | Spain |
| Cat Killer | | |
| Cataloga Incierto | | Argentina |
| Catapult Productions | | |
| Catfish Productions | | United States |
| Catfood Press | | United Kingdom |
| Catorce Index | | |
| Cauchy Productions | | Belgium |
| Cause and Effect | | United States |
| Cause for Concern | | United Kingdom |
| Caustic Tapes | | Canada |
| CDT | | Italy |
| Ce Acatl | | United Kingdom |
| Cedar Creek Sound | | |
| Celestial Harmonies | | |
| Celestial Octaves | | United Kingdom |
| Cellar Tapes | | United Kingdom |
| Centraal Tapes | | Netherlands |
| Central Tapes | | |
| Centrale Dell'Arte & Tasaday | | |
| Centro d’Arte „Laboratorio” | | |
| Chamber Music | | United Kingdom |
| Chamber Tapes | | Japan |
| Channel 5 | | |
| Chaos Network & Records | | |
| Chaos Recordz | | Germany |
| Chaos Tapes | | |
| Charito Records | | |
| Charlotte bill Films | | |
| Charnel House | | |
| Charnel Music | | United States |
| CHBB | | Germany |
| Cheap Tapes International | | |
| Cherry Red | | |
| Chi.Pflug | | Switzerland |
| Chimik Communications | | Canada |
| Chiquita Records | | Germany |
| Chocolate Fireguard | | |
| Chocolate Monk Audio Artifacts | | |
| Chocolate Rabbit Music | | |
| Christus Productions | | Germany |
| Chupa Verga Recordings | | |
| Cinema | | United Kingdom |
| Cinisia Productions | | |
| Cintas | | Spain |
| Circle 9 | | |
| Circle Arts / West | | |
| City Spools | | United Kingdom |
| City Video International | | |
| CKUT | | Canada |
| Clandestine Recordings | | |
| Clear Light Sound | | Canada |
| CLEM Contact List of Electronic Music | | Canada |
| ClicheBootlegCenterTapesRecords&Publicery | | Netherlands |
| Climax Productions | | Belgium |
| Cling Film-Records | | |
| Cloaven Cassettes | | |
| Clockwork Tapes | | |
| Clonaciones Petunio | | Spain |
| Clorex | | |
| Closet Studios | | |
| Club Moral | | Belgium |
| CNLF | | United States |
| Cntmprr-ydtns | | Australia |
| Coach House Press / Music Gallery Talking Books | | Canada |
| CoC | | |
| Code Zero Music | | United States |
| Cohort | | |
| Coiras Clan | | |
| Coitras Clan | | |
| Cold Meat Industry | | Sweden |
| Cold Spring | | |
| Collectif & Cie | | France |
| Collection L'Atta | | France |
