rhythm the basic temporal element of music, concerned with duration and with stresses or accents whether irregular or organized into regular patternings. The formulation in the late 12th cent. of the rhythmic modes—basic recurrent patterns that were adhered to in composition—began the development of the Western system of meter and its notation. Most rhythms are metrical, i.e., the values are multiples of a temporal unit, or beat, usually associated with some particular note value. Free rhythm, such as occurs in much Asian music, has no meter (i.e., its temporal values are not derived from a basic unit). The degree of rhythmic complexity and the types of rhythms used are major considerations in analysis of the style of a composer or a period. The rhythmic tension of music is of value in eliciting emotional response from the hearer. African music and some 20th-century composers employ polyrhythm, the simultaneous use of several rhythmic patterns whose accents do not coincide. See syncopation and metronome .

Bibliography: See P. Kiparsky and G. Youmans, ed., Rhythm and Meter (1989).

RHYTHM
1. The flow and beat of such things as sound, melody, SPEECH, and art
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2. In music, the arrangement of beats and lengths of notes, shown in notation as bars or groups of beats, the first beat of each bar carrying the stress
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3. In poetics, the arrangement of words into a more or less regular sequence of long and short syllables (as in the quantitative metre of LATIN) or stressed and unstressed syllables (as in the accentual metre of English), and any arrangement of this kind
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4. In PHONETICS, the sense of movement in speech, consisting of the STRESS, quantity, and timing of syllables. The rhythm of a language is one of its fundamental features, acquired early by a child and hard for an adult to change. Its basis is pulses of air in the lungs: technically, in the pulmonic airstream mechanism. Such a pulse or beat is produced by the intercostal respiratory muscles and is known as the breath pulse, syllable pulse, or chest pulse. This pulse serves as the basis for the syllable and a flow of such pulses creates the series of beats in the flow of syllables. Occasionally, a pulse can occur but be silent, as when someone says 'kyou for thank you; this is technically referred to as silent stress. When a chest pulse has greater force, it produces a stress pulse whose outcome is usually a stressed SYLLABLE. Ordinary chest pulses occur at a rate of about five per second, stress pulses less frequently. David Abercrombie notes: ‘These two processes—the syllable process and the stress process—together make up the pulmonic mechanism, and they are the basis on which the whole of the rest of speech is built’ (Elements of General Phonetics, 1967, p. 36).

Stress-timed and syllable-timed languages

The two processes are coordinated in different ways in different languages, and the way in which they are combined produces a language's rhythm, which is fundamentally a matter of timing the pulses. In order to account for differences in timing among languages, a distinction is often drawn between stress-timing and syllable-timing, according to whether the foot or the syllable is taken as the unit of time. Broadly speaking, the languages of the world divide into stress-timed languages such as English, Modern GREEK, and RUSSIAN, and syllable-timed languages such as FRENCH and Japanese; many languages, such as Arabic and Hindi, do not fit either category, and it is doubtful whether any language fits either category perfectly. In any language, timing is not uniform throughout speech: it is affected by TONE group boundaries, and slows down in final position. Nevertheless, the distinction is a useful pedagogical device: English learners of French can aim at syllable-timing, and French learners of English can aim at stress-timing. In some styles of delivery, including poetry reading and the recital of the liturgy, the rhythm appears more marked than usual. This is probably due to adjustments to the intonation (such as narrowed pitch range, and tones narrowed to the point where they become level) that background the intonation and leave the rhythm more prominent.

In a stress-timed rhythm, timing is based on stressed syllables that occur at approximately regular (isochronous) intervals: that is, the unit of rhythm known as the foot has about the same duration irrespective of the number of syllables it contains. According to this view, in the phrase //dozens of/ old/ photographs//, dozens of takes about the same time to say as old. In practice, such languages are not strictly isochronous, but rather tend towards it: the syllables of polysyllabic feet are compressed, and monosyllabic feet lengthened. A second feature of such languages is the reduction of unstressed syllables. This applies to the weak syllables of words and unstressed words. In a syllable-timed rhythm, timing is based on the syllable. This does not mean, however, that all syllables are equal in duration: they vary according to the vowels and consonants they contain. Syllable-timed languages lack the rhythmical properties of stress-timing: syllables are not compressed between stresses, and unstressed syllables are not reduced. Although syllable-timing is not used in native-speaker English (except occasionally for comic purposes), it is common in the kind of English spoken by people whose first language is syllable-timed, as is usual in Africa. The consequent lack of reduction might superficially appear to make speech clearer, but by obscuring the stress pattern it reduces the information normally carried by stress and reduces intelligibility. See LINGUISTIC TYPOLOGY, SCHWA, WEAK VOWEL.

rhythm (in the full sense of the word) covers everything pertaining to the time aspect of mus. as distinct from the aspect of pitch, i.e. it incl. the effects of beats, accents, measures, grouping of notes into beats, grouping of beats into measures, grouping of measures into phrases, etc. When all these factors are judiciously treated by the performer (with due regularity yet with artistic purpose—an effect of forward movt.—and not mere machine-like accuracy) we feel and say that the performer possesses ‘a sense of rhythm’. There may be ‘free’ or ‘strict’ rhythm.

The human ear seems to demand the perceptible presence of a unit of time (the beat); even in the ‘free rhythm’ of plainsong this can be felt, though in such mus. the grouping into measures is not present.

Apart from such mus. as that just mentioned it will be found that the beats fall into regular groups of 2s or 3s, or of combinations of these (as a group of 4 made up of 2+2, or a group of 6 made up of 3+3). Such groups or combinations of groups are indicated in our notation by the drawing of bar-lines at regular intervals, so dividing the mus. into measures (or ‘bars’). The measures, in their turn, can be felt to build up into larger groups, or phrases (4 measures to a phrase being a very common but not invariable combination; cf. phrase).

It is chiefly accent that defines these groupings, e.g. taking the larger groupings, a 4-measure phrase is normally accentuated something like this:and if the beats are in any part of the music subdivided into what we may call shorter beat-units sub-accentuations are felt, as Where the measures have 3 beats an accented note is followed by 2 unaccented:and similarly in a 3-measure phrase the first measure will be more heavily accentuated than the 2 following measuresIt will be seen, then, that what we may call the official beat-unit of a composition is a convention, there being often present smaller units and always present larger units, both of which may be considered beats. Another example of free rhythm may be seen in much of the choral mus. of the polyphonic period (madrigals, motets, etc.): these may be said (in literary terms) to be in ‘prose rhythm’, as opposed to the ‘verse rhythm’ of most tunes for marching and dancing.

Just as the traditional conception of tonality dissolved at the beginning of the 20th cent., so the organization of rhythm became more elaborate, irregular, and surprising. It can be divided into 2 categories: (1) metrical, with irregular groups of short units, (2) non-metrical, where there is no perceptible unit of measurement and no ‘traditional’ tempo. Metrical rhythms predominated at the start of the century, but the different uses possible are illustrated by the contrast between Schoenberg's works c.1908–15, where constantly changing tempi and freer use of changing time signatures make the rhythmic structure highly complex, and Stravinsky's of the same period, where there are similar constant changes of time signature but the irregularities are much more clearly defined. Syncopation has also invaded all types of mus. Although syncopated rhythm can be found in the earliest music, in the 20th cent. it has stemmed mainly from jazz.

Non-metrical rhythm can be discerned in Wagner and its possibilities were outlined by Busoni, who wrote of the tense silence between movts. being in itself mus. and more ‘elastic’ than sound. Messiaen in the late 1930s developed ‘ametrical’ rhythm and described in a treatise (1944) that the techniques he used were ‘augmented or diminished rhythms’, ‘retrograde’ rhythms, and ‘polyrhythm’. From 1940 composers such as Babbitt, Boulez, and Messiaen himself developed these tendencies, though some find the results ‘static’ rather than conveying the sense of impetus which is the function of rhythm. Further revolutionary attitudes to rhythm have developed since the 1950s, with the increasing use of indeterminacy. Composers such as Cage, Stockhausen, Carter, and Xenakis have written works which leave the choice of duration and tempo to the performer. With the introduction of elec. and scientific techniques into comp., there seems no limit to the expansion and intricacy of rhythmic procedures in mus.