Frith constructed the music on Accidental using a principle he called "block-melodies"  and he incorporated random events, or "accidents", into the compositions, including "found sounds" and field recordings, to trigger new patterns. Frith explained the background to the making of the album:
I'm fascinated by accidents. When I do solo improvisations I think of myself as being in continuous dialogue with the unexpected, and its always dynamic. Do I ignore this, do I embrace it, do I integrate it, do I keep my distance? When making this music I was constantly using random elements like radio tuning and trying to frame them in metric or harmonic structures.
Bill Tilland of the BBC wrote in a review of this album:
It's fairly standard practice for dance companies to commission "new music" composers to write (and sometimes perform) material for dance performances, and nearly all such work has moments of purely musical interest. But none that I can remember leaves such a strong overall impression as this one. Accidental is a real tribute to Frith's imaginative faculties.