"Barry John Guy (born 22 April 1947, in London) is a British composer and double bass player. His range of interests encompasses early music, contemporary composition, jazz and improvisation, and he has worked with a wide variety of orchestras in the UK and Europe. He also taught at Guildhall School of Music.

Born in London, Guy came to the fore as an improvising bassist as a member of a trio with pianist Howard Riley and drummer Tony Oxley (Witherden, 1969). He also became an occasional member of John Stevens' ensembles in the 1960s and 1970s, including the Spontaneous Music Ensemble. In the early 1970s, he was a member of the influential free improvisation group Iskra 1903 with Derek Bailey and trombonist Paul Rutherford (a project revived in the late 1970s, with violinist Philipp Wachsmann replacing Bailey). He also formed a long-standing partnership with saxophonist Evan Parker, which led to a trio with drummer Paul Lytton which became one of the best-known and most widely travelled free-improvising groups of the 1980s and 1990s. He was briefly a member of the Michael Nyman Band in the 1980s, performing on the soundtrack of The Draughtsman's Contract.

Guy's interests in improvisation and formal composition received their grandest form in the London Jazz Composers Orchestra. Originally formed to perform Guy's composition Ode in 1972 (released as a 2-LP set on Incus and later, in expanded form, as a 2-CD set on Intakt), it became one of the great large-scale European improvising ensembles. Early documentation is spotty - the only other recording from its early years is Stringer (FMP, now available on Intakt paired with the later "Study II") - but beginning in the late 1980s the Swiss label Intakt set out to document the band more thoroughly. The result was a series of ambitious, album-length compositions designed to give all the players in the band maximum opportunity for expression while still preserving a rigorous sense of form: Zurich Concerts, Harmos, Double Trouble (originally written for an encounter with Alexander von Schlippenbach's Globe Unity Orchestra, though the eventual CD was just for the LJCO), Theoria (a concerto for guest pianist Irène Schweizer), Three Pieces, and Double Trouble Two. The group's activities subsided in the mid-1990s, but it was never formally disbanded, and reconvened in 2008 for a one-off concert in Switzerland. In the mid-1990s Guy also created a second, smaller ensemble, the Barry Guy New Orchestra.

Guy has also written for other large improvising ensembles, such as the NOW Orchestra and ROVA (the piece Witch Gong Game inspired by images by the visual artist Alan Davie).

His current improvising activities include piano trios with Marilyn Crispell and Agusti Fernandez. He has also recorded several albums for ECM, which often focus on the interface between improvisers and electronics, including his work in Evan Parker's Electro-Acoustic Ensemble and his own Ceremony.

Guy's session work in the pop field includes playing double bass on the song "Nightporter", from the Japan album Gentlemen Take Polaroids.

He is married to the early music violinist Maya Homburger. After spending some years in Ireland, they now live in Switzerland. They run the small label Maya, which releases a variety of records in the genres of free improvisation, baroque music and contemporary composition.

Guy's jazz work is characterised by free improvisation, using a range of unusual playing methods: bowed and pizzicato sounds beneath the bass's bridge; plucking the strings above the left hand; beating the strings with percussion instrument mallets; and "preparing" the instrument with sticks and other implements inserted between the strings and fingerboard. His improvisations are often percussive and unpredictable, inhabiting no discernible harmonic territory and pushing into unknown regions. However, they can also be melodious and tender with due regard for harmonic integration with other players, and at times he will even play with a straight jazz swing feel.

Similarly, in his concert works, Guy manages to alternate harmonic and rhythmic complexity worthy of 1960s experimentalists such as Penderecki and Stockhausen with joyous, often ecstatic, melody. Works such as "Flagwalk" for string orchestra and "Fallingwater - Concerto for Orchestra" display Guy's compositional skill in handling extended forms and writing for large instrumental groups.

Some of his compositions, such as "Witch Gong Game" for ensemble, use graphic notation in conjunction with cue cards to lead performers into playing and improvising material from numbered sections of the score.

He is also an architect."