Kirsten’s compositions have been played around the world. Brno, for cello and piano, was performed at the Festival OSMOSE in Brussels; Flute Vibes was premiered in Oxford by Chris Britton; the premiere of Remembrance, Journey and Dance (in a version for clarinet, bassoon and piano) was given in New York City by Vent Nouveau; and Union/Disunion, for chamber orchestra, on the UK's leaving of the EU, in London by the London Contemporary Chamber Orchestra in 2017. Most recently, Eliza, was premiered by the Boston New Music Initiative in December 2022.

Kirsten has written for a range of solo instruments, from tuba (Deep Blue) to bassoon (Epik and Dance); for Children's Choir (The Pied Piper of Hamelin); oboe (In simplicity, beauty); SATB choir (The Four Elements); and orchestra (And time stood still....). Her professional work as a pianist includes twenty-four discs of solo piano music for Centaur, Nimbus, Delos and Guild.

Kirsten is a Fellow of the Royal Society of Arts, thersa.org; a Fellow of the Incorporated Society of Musicians, ism.org; and volunteers as Chair of the Board of Directors for the charity Fragile X International (fraxi.org).