"What Is ..." is a high energy experiment in a theme and variations. The theme, heard between rehearsal marks A and B, is more textural rather than melodic. The structure of this theme, and it's variations, also rely on a few sub-themes within the texture. The two sub-themes, parallel minor 3rd / minor triads and a pattern of half and whole steps, can be heard throughout the entire work both on the surface and buried within the structure.