Book excerpt: Variation is a fundamental musical principle, yet its most naked expression - variation form - resists all but the broadest of descriptions. This book offers listener, performer, analyst and composer an eclectic array of approaches to `Theme and Variations', including: patterns of departure and return; real versus perceived time; strategies of propulsion and closure in an intrinsically cyclic and open-ended form; the interplay of authorial voices deriving from dialogue between the `self' of variations and the `other' of their theme; critique of a theme through a set's generic references; drama and narrative achieved through textural and tonal control; and the intrinsic sound of a variation, so different from that of a freely composed work. These topics are introduced through a general survey of the form, seen through the prisms of the provenance of themes and the ideologies of sets, before being developed through close study of Brahms's variation sets and movements. Brahms was supremely aware of his place in music history and was uncommonly self-conscious in his manipulation of different techniques of composition. His variation sets - some of the most well-crafted and beloved examples - place the interplay of forms and styles at the heart of their identity. Moreover, in their stunning breadth and diversity they offer a microcosm of Brahms's entire output, a succinct revelation of his life-long concerns. Through them we marvel at his technical and poetic mastery, and journey to the heart of his creative character.