Editing Rhythm (section)

===Tempo and duration===
{{Further|Tempo|Duration (music)}}

The tempo of the piece is the speed or frequency of the ''tactus'', a measure of how quickly the beat flows. This is often measured in 'beats per minute' ([[Tempo|bpm]]): 60&nbsp;bpm means a speed of one beat per second, a frequency of 1&nbsp;Hz. A [[#Unit and gesture|rhythmic unit]] is a durational pattern that has a period equivalent to a pulse or several pulses.{{sfn|Winold|1975|p=237}} The duration of any such unit is inversely related to its tempo.

Musical sound may be analyzed on five different time scales, which Moravscik has arranged in order of increasing duration.{{sfn|Moravcsik|2002|p=114}}
*Supershort: a single cycle of an audible wave, approximately {{frac|1|30}}–{{frac|1|10,000}} second (30–10,000&nbsp;Hz or more than 1,800&nbsp;bpm). These, though rhythmic in nature, are not perceived as separate events but as continuous [[pitch (music)|musical pitch]].
*Short: of the order of one second (1&nbsp;Hz, 60&nbsp;bpm, 10–100,000 audio cycles). Musical tempo is generally specified in the range 40 to 240 beats per minute. A continuous pulse cannot be perceived as a musical beat if it is faster than 8–10 per second (8–10&nbsp;Hz, 480–600&nbsp;bpm) or slower than 1 per 1.5–2 seconds (0.6–0.5&nbsp;Hz, 40–30&nbsp;bpm). Too fast a beat becomes a [[drone (music)|drone]], too slow a succession of sounds seems unconnected.<ref>{{harvnb|Fraisse|1956}}{{Page needed|date=July 2014}}; {{harvnb|Woodrow|1951}}{{Page needed|date=July 2014}}, both quoted in {{harvnb|Covaciu-Pogorilowski|n.d.}}</ref> This time frame roughly corresponds to the human [[heart rate]] and to the duration of a single step, syllable or [[#Unit and gesture|rhythmic gesture]].
*Medium: ≥ few seconds, this median durational level "defines rhythm in music"{{sfn|Moravcsik|2002|p=114}} as it allows the definition of a rhythmic unit, the arrangement of an entire sequence of accented, unaccented and silent or "[[rest (music)|rest]]" pulses into the [[cell (music)|cells]] of a ''measure'' that may give rise to the "briefest intelligible and self-existent musical unit",{{sfn|Scholes|1977c}} a ''[[motif (music)|motif]]'' or ''[[figure (music)|figure]]''. This may be further organized, by repetition and variation, into a definite ''phrase'' that may characterise an entire genre of music, dance or poetry and that may be regarded as the fundamental formal unit of music.{{sfn|MacPherson|1930|p={{Page needed|date=July 2014}}}}
*Long: ≥ many seconds or a minute, corresponding to a durational unit that "consists of musical phrases"{{sfn|Moravcsik|2002|p=114}}—which may make up a melody, a formal section, a poetic [[stanza]] or a characteristic [[Sequence dance|sequence]] of [[Dance move|dance moves and steps]]. Thus the temporal regularity of musical organisation includes the most elementary levels of [[form (music)|musical form]].{{sfn|MacPherson|1930|p=3}}
*Very long: ≥ minutes or many hours, musical compositions or subdivisions of compositions.

[[Curtis Roads]]{{sfn|Roads|2001}} takes a wider view by distinguishing nine-time scales, this time in order of decreasing duration. The first two, the [[Infinity|infinite]] and the supra musical, encompass natural periodicities of months, years, decades, centuries, and greater, while the last three, the [[sample (music)|sample]] and subsample, which take account of digital and electronic rates "too brief to be properly recorded or perceived", measured in millionths of seconds ([[microsecond]]s), and finally the [[infinitesimal]] or infinitely brief, are again in the extra-musical domain. Roads' Macro level, encompassing "overall musical architecture or [[musical form|form]]" roughly corresponds to Moravcsik's "very long" division while his Meso level, the level of "divisions of form" including [[movement (music)|movements]], [[section (music)|sections]], [[phrase (music)|phrases]] taking seconds or minutes, is likewise similar to Moravcsik's "long" category. Roads' [[Sound object]]:{{Citation needed|date=December 2023}} "a basic unit of musical structure" and a generalization of [[note (music)|note]] ([[Iannis Xenakis|Xenakis']] mini structural time scale); fraction of a second to several seconds, and his [[Microsound]] (see [[granular synthesis]]) down to the threshold of audible perception; thousandths to millionths of seconds, are similarly comparable to Moravcsik's "short" and "supershort" levels of duration.