Cassiel is the pseudonym for London, UK-based composer, performer, software architect and media artist Nick Rothwell. Cassiel projects generally involve collaboration with internationally-renowned choreographers and contemporary dance companies, such as Laurie Booth, Ballett Frankfurt, Russell Maliphant, Lea Anderson, Aydın Teker (İstanbul) and Random Dance Company (Sadler's Wells).

Cassiel plays live sets of pulse-based electronica utilising a variety of control surfaces and custom-designed software performance systems, with a musical style which shifts from Berlin-school to soothing ambient, tribal or glitch, but always with imaginative timbral design and strong harmonic structures. Cassiel has also composed commercially for television, radio and outdoor installations.

Cassiel has worked at STEIM (Amsterdam), CAMAC (Paris), ZKM (Karlsruhe), Techne (İstanbul), Zodiak (Helsinki) and CIANT (Prague). He is a regular performer at the Different Skies festival (Arcosanti, Arizona) and is currently working with dance production company Body>Data>Space in London, Prague, Dresden and Paris.