Kit Downes was born on May 26, 1986, in Norwich, in the east of England. Church music came first: he was an organ scholar at St Peter Mancroft in Norwich, and ECM's notes on his solo organ album name church organ among his earliest musical experiences. He went on to the Purcell School in Bushey, Hertfordshire, and then to the Royal Academy of Music in London, where he studied piano, organ and composition. In his first year at the Academy, 2005, he formed a piano trio with the bassist Calum Gourlay and the drummer James Maddren.

His first recordings were as a sideman. He played on the 2007 debut album of the London quintet Empirical and performed with Acoustic Ladyland, Lee Konitz and the pianist and composer Django Bates. He won the BBC Jazz Award for Rising Star in 2008 and a Yamaha Jazz Scholarship in 2009. The Kit Downes Trio made its debut on record with Golden (Basho, 2009), which was shortlisted for the 2010 Mercury Prize, and followed it with Quiet Tiger (2011) and the quintet album Light from Old Stars (2013), which brought in the clarinettist and tenor saxophonist James Allsopp and the cellist Lucy Railton.

From about 2009 he also played organ and other keyboards in Troyka, a co-operative trio with the guitarist Chris Montague and the drummer Joshua Blackmore that moved between jazz, rock and minimalism. It made Troyka (Edition, 2009), Moxxy (2012) and Ornithophobia, and a big-band version, Troykestra, recorded live at the 2013 Cheltenham Jazz Festival. In the Neon Quartet, with the saxophonist Stan Sulzmann, he made Catch Me (2010) and Subjekt (2012), and with the tenor saxophonist Tom Challenger he recorded the duo album Wedding Music (2013). In 2013 Django Bates asked him to join a new ensemble for a commission for BBC Radio 3 and the Cheltenham festival, and from 2014 he toured with the drummer Benny Greb and co-produced Greb's album Moving Parts.

The organ became the center of his work in the middle of the decade. The Southbank Centre commissioned him in 2014 to write for the opening festival of the refurbished Royal Festival Hall organ, and in 2015 he and Challenger made Vyamanikal, a project for Aldeburgh Music that documented extended techniques on Suffolk church organs. He made his ECM debut that year as the pianist on Thomas Strønen's Time Is a Blind Guide, joined Squarepusher's live band Shobaleader One, and wrote a piece for the organ of the Cologne Philharmonie. An injury to his left hand in 2017 led him to write 52 short piano studies for the right hand alone, one for each day of his recovery. From November 2017 to March 2018 he was part of the ensemble that played and composed for the National Theatre's production of Network.

Obsidian, his first ECM album as a leader, was recorded in November 2016 in three churches (St John the Baptist at Snape, St Edmund at Bromeswell, and the Union Chapel in Islington) and released on January 19, 2018. It is a solo organ record with Challenger joining on one piece. The same year he released the first album by Enemy, his trio with the bassist Petter Eldh and James Maddren, and played on Aidan O'Rourke's year-long tune cycle 365. His organ-led quintet album Dreamlife of Debris followed on ECM in 2019. He won a 2019 DownBeat Critics Poll Rising Star award on both organ and keyboard, a Fellowship of the Royal Academy of Music the same year, and the organ Rising Star category again in 2023.

Since 2020 he has worked in many settings. Subaerial (2021) is a duo with Railton, Vermillion (ECM, 2022) a piano trio with Eldh and Maddren, and Deadeye an organ trio with the guitarist Reinier Baas and the drummer Jonas Burgwinkel. Outpost of Dreams (ECM, 2024), a duo with the singer Norma Winstone, was recorded in April 2023 in Udine, Italy, and produced by Manfred Eicher. He recorded Breaking the Shell as a trio with Bill Frisell and Andrew Cyrille at St Luke in the Fields in New York in May 2022 (it came out in September 2024), and Exhaust, a trio record with the saxophonist Camila Nebbia and the drummer Andrew Lisle, was released in June 2025. A duo album with the drummer Sebastian Rochford, A Short Diary, appeared on ECM in January 2023. He won the Piano/Keyboard Instruments category at the 2025 Deutscher Jazzpreis, and DownBeat described him that summer as living in Berlin. He teaches at the Royal Academy of Music, where he holds his fellowship, and the Royal Conservatoire in The Hague lists him as a piano teacher and artist in residence.

Downes plays in two distinct registers. On piano he is a trio and quintet improviser whose writing and touch connect him to the British school that grew up around the Royal Academy and Basho Records, and Jazzwise has ranked him among the finest pianists of his generation. On organ, both pipe and electric, he works with drones, extended techniques and the quirks of individual church instruments, and ECM's own notes on Obsidian describe a record that sits well outside conventional jazz while depending on an improviser's ear. Troyka and Enemy add rock and electronic energy, and his duos with Challenger and Railton lean toward chamber and experimental music. He also writes for classical ensembles and festivals. His most frequent partners include Challenger, Railton, Eldh, Maddren and Aidan O'Rourke, and his work with Bill Frisell and Andrew Cyrille places him in an American free-leaning tradition as well.