Iso, for viola and piano, was written for pianist Ugne Vazgileviciute and violist Michiel Wittink.

Isorhythm is a musical technique that uses a repeating rhythmic pattern that is applied to a melodic pattern of pitches of the same or different length to the rhythmic pattern. In Iso, three isorhythms of different lengths begin at the same time and repeat continuously, cycling through all possible forms of alignment. Subtle changes in colour and texture occur at points where pairs of isorhythms coincide.