His music has also been described as consisting of "melodious, somewhat Sixties sounds", inspired by an older generation of British experimental composers, such as Michael Parsons. His music exhibits a collage approach, often juxtaposing the sounds of found objects, various kinds of musical material, or snippets of speech. Parkinson himself has described his compositional methods as follows:
What I want beforehand for myself is a large and unforeseen diversity of pitches and intervals – randomness, patterns, shapes – and of course there are countless ways to generate pitches… I’m quite inclusive about what pitches or intervals are presented – I like consonance and dissonance – so sometimes a sequence of notes might be reminiscent of other music, and of course it might not be reminiscent of anything to me, but it might to others… Often I have used the page as a structural unit, like a movement or a panel, and allowed the players to choose their own order of pages for a performance.
Parkinson has also written music for installation art projects, such as sixty eight sounds for Welborne, untitled installation , for a London record shop, and ten brass for St. George's Gardens, Bloomsbury, commissioned by the London Borough of Camden. Much of Parkinson's music has utilitarian titles, such as orchestra piece or is untitled, such as untitled violin and piano and untitled and his official website has the domain name www.untitledwebsite.com. Since 2003, he has been one half of a duo, Parkinson Saunders, with composer James Saunders, performing mostly indeterminate music, using "any sound-producing means", seated at two tables "like newsreaders". Parkinson also performs as solo pianist and occasionally plays with ensembles Apartment House, and Plus-Minus, at venues that have included Tate Modern, the Barbican Centre, and the Huddersfield Contemporary Music Festival.
Parkinson’s opera, Time With People has been widely staged by various international companies, and received performances in London, Huddersfield, Los Angeles, Chicago, Oberlin, Ohio, New York and Brussels. A French translation has been staged in La Chaux-de-Fonds and a German language version is in preparation for 2019. The opera is largely performed without typical musical instruments, on a stage strewn with rubbish, which is also used as a sound source, alongside the sounds of walking, speech, clapping, humming, and musical recordings. It has been described by reviewers as "robotic incantations... scenes of meaningless actions enacted amongst piles of garbage", "theatre of the absurd in eight scenes" and "what opera might be like if you removed music and orchestra".
