As part of a collaborative project between the Staatliches Institut für Musikforschung Preußischer Kulturbesitz and the Audiokommunikation Department of the Technische Universität Berlin, over the course of the last few years we measured – bar by bar – tempi in the first movements of three of Ludwig van Beethoven’s piano sonatas (Appassionata Sonata, Sonata op. 2 Nr. 3, Hammerklavier Sonata) in interpretations from the 1920s through the 2000s. In so doing we examined a series of factors: Have the tempo and shaping of tempo (›Tempogestaltung‹) changed over time? Are there national or culture-specific traditions? Can inter-subjective tempo decisions be identified? How had the shaping of tempi by an individual artist developed over the years and decades? What is the relationship between interpretational practice and the recommendations in the editions prepared by celebrated interpreters?