Expressive timing


Expressive timing refers to the musical phenomenon whereby a performer introduces subtle temporal nuances to an otherwise metronomic interpretation. This is also referred to as microtiming or microrhythm. For instance, a pianist might introduce a slight ritardando at the end of a phrase to convey a structural event. Expressive timing has been shown to operate in different musical styles. In jazz, expressive timing plays an important role in how "swing" eighth-notes are timed.
It has also been shown empirically that simple rhythms are often performed differently from how they are notated. This aspect of rhythm production is at odds with a feature of rhythm perception—namely, that rhythms made up of complex ratios are simplified by listeners to consist of simple ratios. For example, when presented with a sequence of sounds whose interonset intervals are 700 - 300 - 400 milliseconds, a listener might code the rhythm according to the simpler ratios 2:1:1. This is known as quantizing.
The following figure graphs timing data for a short phrase performed by John Coltrane. The Y-axis plots interonset intervals. Even though the notes are nominally sextuplets, notice how their actual durations fluctuate above and below the sextuplet's metronomic value of 162 ms.