If you have endured much 1980s pop music, you might agree that drum machines (pictured) steal the soul from the beat. Their cold regularity is sometimes 'humanized' in the recording studio by the injection of random deviations from precise timing. But that's not good enough, according to Holger Hennig of the Max Planck Institute for Dynamics and Self-Organization in Göttingen, Germany, and his team, who analysed recordings of human drummers and singers performing simple rhythmic patterns.
The researchers find that the rhythmic imperfections of human performers are not statistically independent, but show long-term correlations: one deviation can influence others for tens of seconds afterwards. What's more, listeners prefer rhythms with these correlated defects over those with pure white-noise fluctuations.