Finnis worked with friend Orlando Higginbottom as part of the latter's dance-pop music act, Totally Enormous Extinct Dinosaurs,[7] contributing as co-writer to an album, Trouble released in 2012.[8]
From 2013 to 2016 Finnis was composer-in-association with the London Contemporary Orchestra.[9] They commissioned and premiered several of Finnis' works, including Across White Air for solo cello with reverb, Between Rain for string orchestra, and the electronic piece Colour Field Painting.[2]
Finnis also has a significant association with elderly new music ensemble the London Sinfonietta who have performed, toured and recorded six of his works, including three that they commissioned: Veneer, Unfolds and Seeing is Flux.[10]
Finnis' duo piece for violin and viola, Brother was released as an EP in 2019, on NOMAD records, curated by the band Radiohead's guitarist Jonny Greenwood, who has expressed an enthusiasm for Finnis' work.[11] An album of Finnis' music, The Air, Turning, was also released in February 2019 on NMC Recordings.[1]
Several works by Finnis form the soundtrack to the Icelandic film, Hvítur, Hvítur Dagur ("A White, White Day") which premiered at the 2019 Cannes Film Festival.[12]
Finnis has also contributed string arrangements to albums Goddess (2014)[13] The Altar (2016)[14] by the singer-songwriter Banks.