John Wolf Brennan (born 13 February 1954) is an Irish pianist, organist, melodica player, and composer based in Weggis, Switzerland.
In 1997, he lived in London and worked with Julie Tippetts, Evan Parker, and Chris Cutler in HeXtet, which set to music poems by Seamus Heaney, Edgar Allan Poe, and Theo Dorgan.
Brennan worked with clarinetist Gene Coleman for the Momentum albums and with Christy Doran and Patrice Heral in the group Triangulation, where he developed "comprovisation", a term he coined in 1989.
In 2010, he created the sound installation "Inner & Outer Spaces" with video artist Susanne Hofer for the Lucerne Art Museum, performing with Gerry Hemingway and Thomas K. J. Mejer.
He formed the band Sonic Roots with Christy Doran, Andreas Gabriel, Marc Halbheer, Heiri Kaenzig, and Marcel Oetiker.
For the Alpentöne Festival 2017, he composed "Got hard", an alpine jazz suite for wind orchestra, Pago Libre & Friends (released by Leo Records in 2018).
In August 2018, the Tonhalle Orchester Zürich performed his work Traumpfade with soloists Arkady Shilkloper (alphorn) and Christian Zehnder (overtone voice, global yodeling) at the Festival Stubete am See.