Definition
An irregular grouping divides a value into a number of parts different from the one the meter calls for. In simple meters the natural subdivision is binary (one quarter note = two eighth notes); in compound meters it is ternary (one dotted quarter = three eighth notes). Any grouping that breaks this rule is indicated with a number (and often a bracket or a slur) above or below the notes.
Simple meters (beat = quarter note)
| Grouping | How many notes | In place of | Note value used |
|---|---|---|---|
| Triplet | 3 | 2 eighth notes | eighth notes |
| Quintuplet | 5 | 4 sixteenth notes | sixteenth notes |
| Sextuplet | 6 | 4 sixteenth notes | sixteenth notes |
| Septuplet | 7 | 4 sixteenth notes | sixteenth notes |
| Nonuplet | 9 | 8 thirty-second notes | thirty-second notes |
The writing rule: use the note value of the nearest regular group, rounding down. Five, six or seven notes in the space of a beat are written as sixteenth notes because the reference regular group is four sixteenth notes; from nine to fifteen notes you move to thirty-second notes.
Compound meters (beat = dotted quarter)
| Grouping | How many notes | In place of | Note value used |
|---|---|---|---|
| Duplet | 2 | 3 eighth notes | eighth notes with the number 2 |
| Quadruplet | 4 | 3 eighth notes (or 6 sixteenth notes) | eighth notes |
| Quintuplet | 5 | 6 sixteenth notes | sixteenth notes |
Many editors also write duplets and quadruplets as dotted eighth notes: two dotted eighth notes fill exactly one dotted quarter, so no number is needed. It is a more precise notation and is widespread today.
Sextuplet and double triplet
A true sextuplet is grouped 2+2+2 (six notes in three pairs, accents on 1, 3 and 5); a double triplet is 3+3 (accents on 1 and 4). They are written the same but played with different accentuation: look at the secondary beams and the phrase slurs.
Groupings across several beats
An irregular grouping can occupy several beats: a quarter-note triplet in 4/4 takes up two beats (three quarter notes in place of two). It is a rhythm that “floats” over the pulse and is widely used in pop, soul and film music to create a slowing-down effect without changing tempo.
Practical rules
- To play a quarter-note triplet, think of six eighth-note triplets and accent every other note.
- For a quintuplet think of five syllables of equal length in one beat: “u-ni-ver-si-ty”.
- Always indicate the number if it is not obvious; in long sections you can write “simile” after the first groups.
- In compound meters, if the music often alternates duplets and triplets, consider changing meter (from 6/8 to 2/4 and vice versa).
Typical errors
- Writing a quintuplet in eighth notes because “there are few notes”: the right value is the sixteenth note.
- Playing triplets “limping” (long-short-short) instead of even.
- Confusing an eighth-note triplet with a dotted rhythm: swing is not a written triplet, it is a way of playing.
Examples
- Beethoven, “Moonlight” Sonata, first movement: continuous eighth-note triplets under a melody in binary values.
- Schubert, Erlkönig: the repeated triplets in the piano describe the gallop.
- Debussy, Arabesque No. 1: alternates and superimposes triplets and pairs of eighth notes (two against three).
- Chopin, Nocturnes: embellishments with irregular groupings of many notes (eleven, thirteen, twenty-two) to be distributed freely over the beat.
- In folk-tradition pieces in 6/8 (tarantella, gigue), duplets create brief moments of binary “braking”.
How to use it in composition
- A quarter-note triplet at the end of a phrase creates a written-out ritardando.
- 3 against 2 (triplets in one voice, eighth notes in the other) gives movement and ambiguity without changing tempo.
- In drum parts and fills, quintuplets and sextuplets build energy before a new section.
Exercise
- In 4/4, write a bar with an eighth-note triplet, a sixteenth-note quintuplet, a sextuplet and two eighth notes: check that the values add up.
- In 6/8, write the same melody with duplets and then with dotted eighth notes.
- Tap eighth notes with your right hand and triplets with your left (two against three) for one minute, then swap.
Related topics
Dots, double dots, ties and irregular groupings; Triplets and irregular groupings in the groove; Polyrhythm, hemiola and polymeter; Polyrhythms 3:2, 4:3, 5:4; Time signatures: simple and compound meters.