Parsons' early career began in 1985 with Swans, when he contributed to their Holy Money album. He left Swans in 1987 and joined guitarist Tommy Victor's fledgling Prong. In 1994 he appeared on Buckethead's album Giant Robot. Prong would be Parsons' main project until the group disbanded in 1996. He then started a long-standing friendship with UK composer Justin Broadrick, playing on Godflesh's 1996 tour and their album, Hymns. Parsons has also played in Of Cabbages and Kings with former Swans bandmate Algis Kizys and was a one-time member of Foetus touring band.
Over the years, he has also recorded with members of Public Image Ltd., Legendary Pink Dots, Killing Joke and Gator Bait Ten, a project by Science Slam Sonic Explorers, some of whom appear on his recent NIC remix project album. Youth of Killing Joke contributed a remix based on a Glen Brown/Sylford Walker dub tune. Some music journalists have noted that the cover art on the recent NIC remix album appears to be a homage to early Killing Joke art and design style, in particular referencing the nihilistic anti Imperialist/anti war artwork of Mike Coles of Malicious Damage. Parsons is a frequent member of Broadrick's Jesu project, and has his own dub group, Teledubgnosis.