For this purpose, Keller would construct an analysis in the form of an analytic score written for the same forces as the work under consideration and structured as a succession of 'analytic interludes' designed to be played between its movements.
The focus of such an analysis was the question of how a masterwork could incorporate strongly contrasting ideas and yet still produce the experience of unity and coherence.
Keller's position on this issue was made clear in a number of articles: Functional analysis postulates that contrasts are but different aspects of a single basic idea, a background unityThus his 'FA' scores are designed to demonstrate that the rich 'foreground diversity' of a piece of great music is 'unified' at a 'background' level.
Keller produced more than a dozen of these analytic scores, with the works analysed being by Johann Sebastian Bach, Wolfgang Amadeus Mozart, Joseph Haydn, Ludwig van Beethoven and Benjamin Britten.
His discussion of 'manifest' contrasts and a 'latent' level of unity requiring to be revealed through analysis is explicitly indebted to Sigmund Freud's model of dream-formation, which distinguishes between the 'manifest' content of the dream and the 'latent' dream-thought.