Duration

For other meanings of duration, see: duration (disambiguation).

A duration is an amount of time or a particular time interval. For example, an event in the common sense has a duration greater than zero (but not very long), but in certain specialised senses, a duration of zero. It is often cited as one of the fundamental aspects of music, see also rhythm.

Durations, and their beginnings and endings, may be described as long, short, or taking a specific amount of time. Often duration is described according to terms borrowed from descriptions of pitch. As such, the duration complement is the amount of different durations used, the duration scale is an ordering of those durations from shortest to longest, the duration range is the difference in length between the shortest and longest, and the duration hierarchy is an ordering of those durations based on frequency of use (DeLone et. al. (Eds.), 1975, chap. 3).

Durational patterns are the foreground details projected against a background metric structure, which includes meter, tempo, and all rhythmic aspects which produce temporal regularity or structure. Duration patterns may be divided into rhythmic units and rhythmic gestures. (DeLone et. al. (Eds.), 1975, chap. 3) However, they may also be described using terms borrowed from the metrical feet of poetry: iamb (weak-strong), anapest (weak-weak-strong), trochee (strong-weak), dactyl (strong-weak-weak), and amphibrach (weak-strong-weak), which may overlap to explain ambigouity (Cooper and Meyer, 1960).

Curtis Roads (2001, p.3-4) distinguishes nine time scales of music:

1. Infinite: literally infinite, such as the length of sine waves in classical Fourier analysis,
2. Supra: months, years, decades, and centuries; everything above the level of
3. Macro: "overall musical architecture or form" or the level of the individual piece; minutes, hours, or even days,
4. Meso: "Divisions of form" including movements, sections, phrases; seconds and minutes,
5. Sound object: "a basic unit of musical structure" and a generalization of note; fraction of a second to several seconds,
6. Micro: "sound particles" down to the threshold of audible perception; thousands to millionths of seconds,
7. Sample: sample (music), measured as are samples in millionths of a second or microseconds,
8. Subsample: changes "too brief to properly recorded or perceived", billionths of a second, nanosecond, or less, and
9. Infinitesimal: literally "infinitely brief" such as delta functions.