Polyrhythm is the simultaneous use of two or more conflicting rhythms, that are not readily perceived as deriving from one another, or as simple manifestations of the same meter. The rhythmic conflict may be the basis of an entire piece of music (cross-rhythm), or a momentary disruption. Polyrhythms can be distinguished from irrational rhythms, which can occur within the context of a single part; polyrhythms require at least two rhythms to be played concurrently, one of which is typically an irrational rhythm.
In some European art music, polyrhythm periodically contradicts the prevailing meter. For example, in Mozart's opera Don Giovanni, two orchestras are heard playing together in different metres (3
4 and 2
They are later joined by a third band, playing in 3
It is a particularly common feature of the music of Brahms. Writing about the Violin Sonata in G major, Op. 78, Jan Swafford (1997, p. 456) says "In the first movement Brahms plays elaborate games with the phrasing, switching the stresses of the 6
4 meter back and forth between 3+3 and 2+2+2, or superimposing both in violin and piano. These ideas gather at the climax at measure 235, with the layering of phrases making an effect that perhaps during the 19th century only Brahms could have conceived."
In "The Snow is Dancing" from his Children's Corner suite, Debussy introduces a melody "on a static, repeated B-flat, cast in triplet-division cross rhythms which offset this stratum independently of the sixteenth notes comprising the two dancing-snowflake lines below it." "In this section great attention to the exactitude of rhythms is demanded by the polyrhythmic superposition of pedals, ostinato, and melody."
Concerning the use of a two-over-three (2:3) hemiola in Beethoven's String Quartet No. 6, Ernest Walker states, "The vigorously effective Scherzo is in 3
4 time, but with a curiously persistent cross-rhythm that does its best to persuade us that it is really in 6
However, the two beat schemes interact within a metric hierarchy (a single meter). The triple beats are primary and the duple beats are secondary; the duple beats are cross-beats within a triple beat scheme.
Cross-rhythm refers to systemic polyrhythm. The New Harvard Dictionary of Music states that cross-rhythm is: "A rhythm in which the regular pattern of accents of the prevailing meter is contradicted by a conflicting pattern and not merely a momentary displacement that leaves the prevailing meter fundamentally unchallenged" (1986: 216). The physical basis of cross-rhythms can be described in terms of interference of different periodicities.
A simple example of a cross-rhythm is 3 evenly spaced notes against 2 (3:2), also known as a hemiola. Two simple and common ways to express this pattern in standard western musical notation would be 3 quarter notes over 2 dotted quarter notes within one bar of 6
8 time, quarter note triplets over 2 quarter notes within one bar of 2
4 time. Other cross-rhythms are 4:3 (with 4 dotted eight notes over 3 quarter notes within a bar of 3
4 time as an example in standard western musical notation), 5:2, 5:3, 5:4, etc.
There is a parallel between cross rhythms and musical intervals: in an audible frequency range, the 2:3 ratio produces the musical interval of a perfect fifth, the 3:4 ratio produces a perfect fourth, and the 4:5 ratio produces a major third. All these interval ratios are found in the harmonic series. These are called harmonic polyrhythms.
In traditional European ("Western") rhythms, the most fundamental parts typically emphasize the primary beats. By contrast, in rhythms of sub-Saharan African origin, the most fundamental parts typically emphasize the secondary beats. This often causes the uninitiated ear to misinterpret the secondary beats as the primary beats, and to hear the true primary beats as cross-beats. In other words, the musical "background" and "foreground" may mistakenly be heard and felt in reverse--Peñalosa (2009: 21).
In non-Saharan African music traditions, cross-rhythm is the generating principle; the meter is in a permanent state of contradiction. Cross-rhythm was first explained as the basis of non-Saharan rhythm in lectures by C.K. Ladzekpo and the writings of David Locke.
From the philosophical perspective of the African musician, cross-beats can symbolize the challenging moments or emotional stress we all encounter. Playing cross-beats while fully grounded in the main beats, prepares one for maintaining a life-purpose while dealing with life's challenges. Many non-Saharan languages do not have a word for rhythm, or even music. From the African viewpoint, the rhythms represent the very fabric of life itself; they are an embodiment of the people, symbolizing interdependence in human relationships--Peñalosa (2009: 21).
At the center of a core of rhythmic traditions within which the composer conveys his ideas is the technique of cross-rhythm. The technique of cross-rhythm is a simultaneous use of contrasting rhythmic patterns within the same scheme of accents or meter... By the very nature of the desired resultant rhythm, the main beat scheme cannot be separated from the secondary beat scheme. It is the interplay of the two elements that produces the cross-rhythmic texture--Ladzekpo (1995).
Eugene Novotney observes: "The 3:2 relationship (and [its] permutations) is the foundation of most typical polyrhythmic textures found in West African musics." 3:2 is the generative or theoretic form of non-Saharan rhythmic principles. Victor Kofi Agawu succinctly states, "[The] resultant [3:2] rhythm holds the key to understanding... there is no independence here, because 2 and 3 belong to a single Gestalt."
The two beat schemes interact within the hierarchy of a single meter. The duple beats are primary and the triple beats are secondary. The example below shows the African 3:2 cross-rhythm within its proper metric structure.
The music of African xylophones, such as the balafon and gyil, is often based on cross-rhythm. In the following example, a Ghanaian gyil sounds a 3:2-based ostinato melody. The left hand (lower notes) sounds the two main beats, while the right hand (upper notes) sounds the three cross-beats. The cross-beats are written as quarter-notes for visual emphasis.
The following notated example is from the kushaura part of the traditional mbira piece "Nhema Mussasa". The mbira is a lamellophone. The left hand plays the ostinato bass line while the right hand plays the upper melody. The composite melody is an embellishment of the 3:2 cross-rhythm.
Sub-Saharan instruments are constructed in a variety of ways to generate polyrhythmic melodies. Some instruments organize the pitches in a uniquely divided alternate array, not in the straight linear bass to treble structure that is so common to many western instruments such as the piano, harp, or marimba.
Lamellophones including mbira, mbila, mbira huru, mbira njari, mbira nyunga, marimba, karimba, kalimba, likembe, and okeme. This family of instruments are found in several forms indigenous to different regions of Africa and most often have equal tonal ranges for right and left hands. The kalimba is a modern version of these instruments originated by the pioneer ethnomusicologist Hugh Tracey in the early 20th century which has over the years gained worldwide popularity.
Chordophones, such as the West African kora, and doussn'gouni, part of the harp-lute family of instruments, also have this African separated double tonal array structure.[clarification needed]Another instrument, the Marovany from Madagascar is a double sided box zither which also employs this divided tonal structure.
The Gravikord is a new American instrument closely related to both the African kora and the kalimba was created in the latter 20th century to also exploit this adaptive principle in a modern electro-acoustic instrument.
On these instruments, one hand of the musician is not primarily in the bass nor the other primarily in the treble, but both hands can play freely across the entire tonal range of the instrument. Also, the fingers of each hand can play separate independent rhythmic patterns, and these can easily cross over each other from treble to bass and back, either smoothly or with varying amounts of syncopation. This can all be done within the same tight tonal range, without the left and right hand fingers ever physically encountering each other. These simple rhythms will interact musically to produce complex cross rhythms including repeating on beat/off beat pattern shifts that would be very difficult to create by any other means. This characteristically African structure allows often simple playing techniques to combine with each other to produce polyrhythmic music.
Polyrhythm is a staple of modern jazz. Although not as common, use of systemic cross-rhythm is also found in jazz. In 1959, Mongo Santamaria recorded "Afro Blue", the first jazz standard built upon a typical African 6:4 cross-rhythm (two cycles of 3:2). The song begins with the bass repeatedly playing 6 cross-beats per each measure of 12
8 (6:4). The following example shows the original ostinato "Afro Blue" bass line. The cross noteheads indicate the main beats.
The famous jazz drummer Elvin Jones took the opposite approach, superimposing two cross-beats over every measure of a 3
4 jazz waltz (2:3). This swung 3
4 is perhaps the most common example of overt cross-rhythm in jazz. In 1963 John Coltrane recorded "Afro Blue" with Elvin Jones on drums. Coltrane reversed the metric hierarchy of Santamaria's composition, performing it instead in 3
4 swing (2:3).
Nigerian percussion master Babatunde Olatunji arrived on the American music scene in 1959 with his album Drums of Passion, which was a collection of traditional Nigerian music for percussion and chanting. The album stayed on the charts for two years and had a profound impact on jazz and American popular music. Trained in the Yoruba sakara style of drumming, Olatunji would have a major impact on Western popular music. He went on to teach, collaborate and record with numerous jazz and rock artists, including Airto Moreira, Carlos Santana and Mickey Hart of the Grateful Dead. Olatunji reached his greatest popularity during the height of the Black Arts Movement of the 1960s and 1970s.
Afro-Cuban music makes extensive use of polyrhythms. Cuban Rumba uses 3-based and 2-based rhythms at the same time, for example, the lead drummer (playing the quinto) might play in 6
8, while the rest of the ensemble keeps playing 2
2. Afro-Cuban conguero, or conga player, Mongo Santamaría was another percussionist whose polyrhythmic virtuosity helped transform both jazz and popular music. Santamaria fused Afro-Latin rhythms with R&B and jazz as a bandleader in the 1950s, and was featured in the 1994 album Buena Vista Social Club, which was the inspiration for the like-titled documentary released five years later.
Among the most sophisticated polyrhythmic music in the world is south Indian classical Carnatic music. A kind of rhythmic solfege called konnakol is used as a tool to construct highly complex polyrhythms and to divide each beat of a pulse into various subdivisions, with the emphasised beat shifting from beat cycle to beat cycle.
Common polyrhythms found in jazz are 3:2, which manifests as the quarter-note triplet; 2:3, usually in the form of dotted-quarter notes against quarter notes; 4:3, played as dotted-eighth notes against quarter notes (this one demands some technical proficiency to perform accurately, and was not at all common in jazz before Tony Williams used it when playing with Miles Davis); and finally 3
4 time against 4
4, which along with 2:3 was used famously by Elvin Jones and McCoy Tyner playing with John Coltrane.
Frank Zappa, especially towards the end of his career, experimented with complex polyrhythms, such as 11:17, and even nested polyrhythms (see "The Black Page" for an example). The metal bands Meshuggah, Nothingface, Periphery, Threat Signal, Lamb of God, Textures and TesseracT also use polyrhythms in their music. Contemporary progressive metal bands such as Mudvayne, Tool, Animals as Leaders, Between the Buried and Me and Dream Theater also incorporate polyrhythms in their music, and polyrhythms have also been increasingly heard in technical metal bands such as Ion Dissonance, The Dillinger Escape Plan, Necrophagist, Candiria, The Contortionist and Textures. Much minimalist and totalist music makes extensive use of polyrhythms. Henry Cowell and Conlon Nancarrow created music with yet more complex polytempo and using irrational numbers like ?:e.
Nine Inch Nails front man Trent Reznor uses polyrhythm frequently. One notable appearance is in the song "La Mer" from the album The Fragile. The piano holds a 3
4 riff while the drums and bass back it with a standard 4
Megadeth frequently tends to use polyrhythm in its drumming, notably from songs such as "Sleepwalker" or the ending of "My Last Words", which are both played in 2:3.
Japanese girl group Perfume made use of the technique in their single, appropriately titled "Polyrhythm", included on their second album Game. The bridge of the song incorporates 5
8 in the vocals, common time (4
4) and 3
2 in the drums.
The Aaliyah song "Quit Hatin" uses 9
8 against 4
4 in the chorus.
The Japanese idol group 3776 makes use of polyrhythm in a number of their songs, most notably on their 2014 mini-album "Love Letter", which features five songs that all include several rhythmic references to the number 3776. A secret track on the album has the group's leader, Ide Chiyono, explain some of the uses of polyrhythm to the listener.
The following is an example of a 3 against 2 polyrhythm, given in time unit box system (TUBS) notation; each box represents a fixed unit of time; time progresses from the left of the diagram to the right. It is in bad form to teach a student to play 3:2 polyrhythms as simply quarter note, eighth note, eighth note, quarter note. The proper way is to establish sound bases for both the quarter-notes, and the triplet-quarters, and then to layer them upon each other, forming multiple rhythms. Beats are indicated with an X; rests are indicated with a blank.
A common memory aid to help with the 3 against 2 polyrhythm is that it has the same rhythm as the phrase "not difficult"; the simultaneous beats occur on the word "not"; the second and third of the triple beat land on "dif" and "cult", respectively. The second 2-beat lands on the "fi" in "difficult". Try saying "not difficult" over and over in time with the sound file above. This will emphasize the "3 side" of the 3 against 2 feel. Now try saying the phrase "not a problem", stressing the syllables "not" and "prob-". This will emphasize the "2 side" of the 3 against 2 feel. More phrases with the same rhythm are "cold cup of tea", "four funny frogs", "come, if you please".
Similar phrases for the 4 against 3 polyrhythm are "pass the golden butter" or "pass the goddamn butter" and "what atrocious weather" (or "what a load of rubbish" in British English); the 4 against 3 polyrhythm is shown below.
As can be seen from above, the counting for polyrhythms is determined by the lowest common multiple, so if one wishes to count 2 against 3, one needs to count a total of 6 beats, as lcm(2,3) = 6 (123456 and 123456). However this is only useful for very simple polyrhythms, or for getting a feel for more complex ones, as the total number of beats rises quickly. To count 4 against 5, for example, requires a total of 20 beats, and counting thus slows the tempo considerably. However some players, such as classical Indian musicians, can intuitively play high polyrhythms such as 7 against 8.
Polyrhythms are quite common in late Romantic Music and 20th century classical music. Works for keyboard often set odd rhythms against one another in separate hands. A good example is in the soloist's cadenza in Grieg's Concerto in A Minor; the left hand plays arpeggios of seven notes to a beat; the right hand plays an ostinato of eight notes per beat while also playing the melody in octaves, which uses whole notes, dotted eighth notes, and triplets. Other instances occur often in Rachmaninoff's Piano Concerto No. 2. The piano arpeggios that constitute much of the soloist's material in the first movement often have anywhere from four to eleven notes per beat. In the last movement, the piano's opening run, marked 'quasi glissando', fits 52 notes into the space of one measure, making for a glissando-like effect while keeping the mood of the music. Other instances in this movement include a scale that juxtaposes ten notes in the right hand against four in the left, and one of the main themes in the piano, which imposes an eighth-note melody on a triplet harmony.