The word 'Shape-sorter' refers to a popular toy for young children, which involves fitting a selection of different shapes into their equivalent holes. It is a very traditional form of childhood entertainment and found in many family homes - my own two year-old daughter Hazel has enjoyed hers as a particular favourite.

In this piece there are ten themes: five shapes, and five holes. The themes all feature in various guises throughout the eight minutes of music, the shapes with a degree of flexibility, the holes more resolutely stable. These themes are conceived in pairs, so that when a shape theme meets its equivalent hole theme and they are aligned and rotated correctly and at the right speed, they fit together; this releases a 'success cadence' and the shape theme disappears from the music.