He was a member of the English avant-rock group Henry Cow and founded several bands himself, including Red Balune, Random Bob, Black Sheep, Mirage, and Ex-Wise Heads.

In 1969 he joined G. F. Fitzgerald's band Mouseproof, which introduced Leigh to the budding Canterbury scene and musicians like Daevid Allen, Kevin Ayers, and Robert Wyatt.

In November 1973, Leigh participated in a live-in-the-studio performance of Mike Oldfield's Tubular Bells for the BBC, with Mick Taylor, Steve Hillage and members of Henry Cow, Gong and Soft Machine.

Red Balune grew over the next few years and attracted a number of musicians, including Colin McClure (bass), Robin Musgrove (drums), Henk Weltevreden (keyboards), Aloijsius van Saus (industrial sounds and performance), and Anne-Marie Roeloffs (trombone).

[2] In April 1978 the band relocated to the Netherlands, recording the EP Maximum Penalty in early 1979, which featured guest appearances by ex-Henry Cow members Fred Frith (guitar, violin), Tim Hodgkinson (keyboards, alto saxophone, clarinet), Chris Cutler (piano scrapes and general burning ideas), and Aksak Maboul founder Marc Hollander (bass clarinet).

After leaving the Black Sheep in 1982, Leigh formed several bands which owed more to world music than any of his previous work, the most long-standing being Random Bob, featuring Colin McClure, Henk Weltevreden, and percussionist Asad Oberoi, later replaced by drummer/percussionist Coen Aalberts.

In 1986, Leigh headed back to Brussels, where he became even more closely involved in the world music scene, performing with Algerian singer Hamsy Boubaker, and Moroccan oud players Hassan Erragi and Abid.

With Abid he co-composed and performed the music for a one-woman theatre production with Tunisian-Belgian actress Sabra Ben Arfa, produced by Moroccan actor-producer Amid Chakir, a close associate of Belgian film maker Chantal Akerman.

Leigh played with Pierre Jacob (keyboards, flutes, percussion, vocals) in the fusion group Sables from 1988 until 1992, and in 1988 formed the Morton Fork Gang with British saxophonist Joe Higham – the band included Daniel Denis (drums) and Guy Segers (bass guitar) from Univers Zéro, cellist Jan Kuijken, and saxophonists Mark Bogaerts and Daniel Stokart.

He managed to fulfil some concert obligations with Morton Fork and Sables in Brussels in early 1993, and after returning permanently to the UK, rehearsed and performed in small venues with original Radar Favourites bassist Jack Monck and Moroccan percussionist Lahcen Lahbib, as the Highly Irregulars.

A chance meeting in 2002 with Berliner Tom Zunk (waterphone and Indonesian percussion) led to the formation of the duo Men Working Overhead, which performed several concerts in Germany and London between 2002 and 2004, often augmented by dancer-video artist Elke Postler.

Other activities in 2009 included a solo performance at the Kraak Festival in Brussels in March, five concerts and two workshops in Japan with Yumi Hara, plus a guest appearance with Japanese psychedelic rock band Acid Mothers Temple.

In August, Leigh performed at the annual Avant Garde Festival in Schiphorst, Germany, with Yumi Hara and ex–Henry Cow members Chris Cutler (drums) and John Greaves (bass and vocals), which led to them forming The Artaud Beats.

In late October 2009, Leigh played solo at the Nodutgang Festival in Bodo, Norway, and several concerts in Sweden with Magnus Alexanderson (guitar and electronics).

Three new albums were released: Radar Favourites, Ex Wise Heads, and Uwe Bastiansen's Stadtfischflex, featuring Leigh alongside Jean–Herve Peron and Zappi Diermaier (Faust), and Tim Hodgkinson (Henry Cow).

2015 – Concert/radio broadcast in Rome (Italy) with K–Mundi Trio (Adriano Lanzi, Filippo Okapi, and Marco Ariano); The Artaud Beats present their new album Logos at Le Triton in Paris; Leigh plays a festival in Lille (France) with Max Manach, Valentin Carette, and Ciro Martin as "Haricot Massacre".

Concerts in London include a trio with Max Manac'h and Jean–Herve Peron, and various combinations with Yumi Hara, Guy Harries, Chris Cutler, and Tim Hodgkinson.