By the end of 1978, Leith joined up with Farrelly, Finnis and another person to form a school 'supergroup' named Matt Vinyl and the Emulsions, inspired by the punk ethos.

After their second gig at the Peartree Bridge Centre went badly, they decided to look beyond the confines of Milton Keynes and recorded their first demo at The Crypt, an eight-track studio in Stevenage, in January 1981.

Another demo, In the Shadow of the Cross, was recorded in spring that year and garnered attention from the thriving underground network of zines and like-minded individuals including Andy Martin of the Apostles.

[7] Part 1 released the Funeral Parade EP in October 1982 on their own Paraworm Records and played their final show in April 1983, supporting the Subhumans at Oxford Street's 100 Club, where Leith split his bass drum skin.

[9] Leith was the singer and drummer in the progressive pop band Ad Nauseam with guitarist Jon Poole,[10][11][12][13] which had elements of Genesis and '80s rock.

[16][a] Afterwards Poole tried to keep Ad Nauseam going but the band was torn apart by internal arguments, power struggles and jealousy; he vowed that he would come back for Leith and get him in Cardiacs but the two didn't talk for a year.

[2] Their song "Building Cakes" was included on the 2001 compilation Cardiacs and Affectionate Friends, as Catherine in a Cupboard, and an album was in the making that was to be released on the recording label All My Eye and Betty Martin Music.

[17] With a four-piece lineup up of Tim, Jim, Leith and newly welcomed guitarist Kavus Torabi replacing Poole, the best takes from the three-night stand were released in the two-hour 2005 live album The Special Garage Concerts as two different volumes.

[44] A surrealist vein runs through the footage: the band is crammed into a tiny shack and constantly get in each other's way with Jim playing in his underwear fighting for space against one of Leith's cymbals not in use.

[45] He made his debut with Blurt at the 2004 Glastonbury Festival's Friday JazzWorld Stage[46] and recorded the tracks "Sweet Thames", "Hat" and "Cut It!"

[48] In 2005, Cardiacs' shows saw the group add three additional singers and two percussionists: Cathy Harabaras and Dawn Staple, to the lineup, who contributed drums with Leith.

[49] The extra percusion is featured on the 2007 single "Ditzy Scene" as Leith pounds a bass drum rhythm accompanied by a steady tambourine.

[43] On the single "Vermin Mangle", released digitally exclusively on Bandcamp after Smith's death in 2020 and likely from LSD, Leith acts the band's ever-present heartbeat for the percussion with Harabaras and Woods playing around his rhythm in fun and musical ways, according to Benac.

[55] He guests on most tracks of Crayola Lectern's 2013 album The Fall and Rise of... which also includes Poole and Hayes,[56] and featured in Mark Cawthra's psychedelic rock band Redbus Noface at Salisbury Arts Centre in 2016.

[57] The 2018 double album Real Estate/Fake Inverno by the Italian pop group Sterbus was made in cahoots with Leith and features his permanent presence in a guest appearance.

[63][64] Following the gigs, four October dates were announced and Cardiacs performed a live session on Marc Riley and Gideon Coe’s BBC Radio 6 Music show, broadcast on 17 June.

[10] Eric Benac called Leith "a precise drummer possessed of a skilled musical mind" who "had a strong way with words" and "the missing puzzle piece" that Cardiacs needed to move forward as a power quartet.

[19] Benac noted how Leith's use of wordplay and "youthful sense of adventure and enthusiasm" in his lyrics made him a good foil for Tim Smith.