After a nomadic early childhood moving from town to town, Ellis' family settled in Anglesey, eventually moving to London where he studied at the Royal Academy of Music and worked with numerous bands through a myriad of genres.
Among the artists that Ellis has collaborated or performed with are Edwyn Collins, Sarah Cracknell, The Pretenders, Oasis, Shane MacGowan, UNKLE, North Mississippi Allstars, James Hunter, Roddy Frame, Paul Cook (Sex Pistols), Thee Hypnotics, Barrie Cadogan (Little Barrie), The 2 Bears, Alex Kapranos and Nicholas McCarthy (Franz Ferdinand), Romeo Stodart (The Magic Numbers), The Drums, Ian Siegal, Pete Molinari, Fabienne Delsol, Gemma Ray, Quruli and Lay Low.
After having established himself as a session musician in London, in 2008 Ellis moved to Cardiff, emerging as a frontman in his own right and calling his band Colorama. They released their Japan-only debut album Cookie Zoo on Noise McCartney in April 2008, and released their debut single Sound via Redbricks Recordings in July 2008.
In 2009, Colorama announced that their double bass player, Ellis's best friend David Fletcher, had died at the age of 37 on 29 June, from a heart attack suffered in his sleep, just days after Colorama’s appearance at Glastonbury Festival.
September 2009 saw the UK release of Colorama's album Magic Lantern Show on Redbricks Recordings, featuring songs in Welsh and English. Magic Lantern Show was enthusiastically received with extensive radio play on XFM, BBC 6 Music, BBC Radio 1, BBC Radio Wales, C2 and BBC Radio Cymru.
Early in 2010, Ellis joined forces with Shane MacGowan, Nick Cave, Bobby Gillespie, Chrissie Hynde, Mick Jones, Glen Matlock, Paloma Faith, Cait O'Riordan, Johnny Depp, James and Robert Walbourne, to release a charity single covering the Screamin' Jay Hawkins hit I Put A Spell On You. All the proceeds from the single went to Concern Worldwide to provide assistance to the victims of the earthquake that devastated Haiti.
In autumn 2010, Ellis released Colorama's third album BOX on Noise McCartney / Bad News Records (Victor Entertainment) in Japan and via See Monkey Do Monkey Recordings in UK. Shortly afterwards, they released a Christmas single, Cerdyn Nadolig (Christmas Card), which garnered them the Welsh Christmas Number 1 on the BBC Radio Cymru chart. BOX was also nominated for the inaugural Welsh Music Prize.
Amid other projects, Ellis produced and arranged Italian artist Emma Tricca's album Minor White, which was released on Finders Keepers / Bird Records in the UK, and he worked with French artist Fabienne Delsol on her album ON MY MIND (Damaged Goods), also Dan Sartain's album Dan Sartain Lives (One Little Indian Records), The Keys' album - Fire Inside (See Monkey Do Monkey Recordings) and Edwyn Collins' album Losing Sleep (Heavenly Recordings).
In October 2011, Colorama released Llyfr Lliwio (Colouring Book), which was their first predominantly Welsh-language collection. During this period Ellis was a member of Roddy Frame's touring band.
August 2012 saw their fifth album release - Good Music, produced by Edwyn Collins and Sebastian Lewsley, and released on Collins’s new AED Records label, followed by a 12-inch single, Hapus? (Happy?), on Aficionado Recordings in November 2012.
In autumn 2012, Ellis toured Asia playing keyboards, guitar and percussion with the Pretenders.
In 2013, Ellis focused on studio work, recording with Edwyn Collins, Gemma Ray, Roddy Frame and in early 2014, Japanese artists Quruli. He also produced and arranged the second album, Relic for Emma Tricca, released by Finders Keepers / Bird Records in May 2014 and co-produced the first album by Nev Cottee, Stations (Roleplay Records).
In 2014, Colorama released a new EP, Heaven's Hotel, a new album TEMARI, followed by a split single, Yn Rhydiau'r Afon / Forget Tomorrow with The Joy Formidable.
A compilation of all of Ellis's Welsh songs as Colorama was released in November 2014, entitled Dere Mewn!, on his own, new Agati label.
Ellis collaborated with Edwyn Collins and Seb Lewsley on the soundtrack to the film The Possibilities Are Endless, composing much of its original score, which opened in October 2014 to great critical success, winning the Mojo 'Film Of The Year' Award.
February 2015 saw Ellis release his first album as Zarelli, Soft Rains on the Seriés Aphōnos label– a mostly instrumental synthesizer record, featuring the voice of Leonard Nimoy reading the Ray Bradbury short story There Will Come Soft Rains. Soft Rains received a nomination for the Welsh Music Prize 2015.
In June 2015 the LP Red Kite by Sarah Cracknell of Saint Etienne was released, which was co-produced, co-written and arranged by Ellis. A single, Nothing Left To Talk About (featuring Nicky Wire of Manic Street Preachers) reached Number 1 in the UK vinyl singles chart on its release.
Early in 2016, Ellis began presenting a weekly radio show, X Marks The Spot on Soho Radio in London.
A Welsh language collaborative album, Bendith made by Carwyn Ellis with the folk trio, Plu is due for release on Ellis's Agati label in October 2016.
