Onset‐to‐onset durations of quarter notes and sixteenth notes were ‘measured in nineteen complete performances of the third movement of Beethoven's Piano Sonata op. 31, No. 3. These measurements were compared to those from a computer performance incorporating the “Beethoven pulse” expressive microstructure devised by Manfred Clynes [U.S. Patent No. 4,704,682 (1987)]. This pulse is a particular pattern of relative note durations (and amplitudes) within successive time units, and it is designed to be invariant except for occasional larger deviations at structurally salient points. Although patterns resembling the Beethoven pulse could be found locally in the human performances, on the whole there was little evidence for a fixed, pulselike pattern of timing deviations. Rather, the measurements suggest that great artists change the patterns of relative note durations continuously to meet the local expressive requirements of the composition, and that, despite considerable individual differences, there is some consensus about what these requirements are. If the invariant Beethoven pulse enhances the expressiveness of the computer performance, as it seems to do [B. H. Repp, J. Acoust. Soc. Am. Suppl. 181, S92 (1987)], this is apparently not because it captures aspects of human performance. [Work supported by NIH.]