The nature and perception of fluctuations in human musical rhythms

handsHave you ever wondered why music generated by computers and rhythm machines sometimes sounds unnatural? One reason for this is the absence of small inaccuracies that are part of every human activity. Professional audio software therefore offers a so-called humanizing technique, by which the regularity of musical rhythms can be randomized to some extent.

But what exactly is the nature of the inaccuracy in human musical rhythms? Studying this question for the first time, we found that the temporal rhythmic fluctuations exhibit scale-free long-range correlations, i.e., a small rhythmic fluctuation at some point in time does not only influence fluctuations shortly thereafter, but even after tens of seconds. While this characterization is relevant for neurophysiological mechanisms of timing, it also leads to a novel concept for humanizing musical sequences. Comparing with conventionally humanized versions listeners showed a high preference for long-range correlated humanized music over uncorrelated humanized music. (Photo: Courtesy of Agbenyega Attiogbe-Redlich,

Original article (Free download): H. Hennig, R. Fleischmann, A. Fredebohm, Y. Hagmayer, J. Nagler, A. Witt, F.J. Theis, T. Geisel, PLoS ONE 6(10): e26457 (2011).

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Audio examples

These and more humanized audio examples can be found in the audio gallery.

J.S. Bach, Invention no.1 in C major, BWV 772

Bach Invention1


J.S. Bach, Prelude no. 2 in C minor (Well-tempered Clavier Vol. II, BWV 871)

bach Prelude 2




Online survey

Here you can experience how humanization sounds when applied to the music of J.S. Bach: View survey results