Duration, Rhythm & Meter

A photograph of two women holding the two ends of a jump rope while a girl jumps between them and several dozen other children look on. Children jump rope on a playground in Uganda in 2018. Children often use rhythmic chants when jumping rope, which are performed to the rhythm of the spinning ropes.
(Danny Shots | CC BY-SA-4.0)

Unlike painting or sculpture, music is a temporal art: works unfold over time, interacting with the listener's memories and expectations within both long-term and immediate timeframes.

Rhythm

Rhythm is the placement in time of a consecutive group of sounds, like the notes of a melody, the spoken syllables of a conversation, or the footfalls of a galloping horse. Rhythms can take many different forms, as intentional artistic designs or barely-noticed side effects, occurring as lengthy patterns of repetition or in short bursts of sound.

The two basic components of rhythm are an individual sound's attack or onset, the time at which a sound begins, and its duration, the amount of time a sound persists before stopping.

A diagram showing each syllable of the audio of James Shaw saying `kudos to people like, like Trent Reznor` with the beginnings of each syllable labeled as `attacks` and the measured length of each syllable labelled as `durations.`
Figure 1: An excerpt from an interview of Canadian singer/songwriter James Shaw showing the attacks and duration of each syllable.
(Uncensored Interview | CC BY-3.0)

Measured Rhythm

Many of the sounds we hear around us have unmeasured or unintentional rhythm: a rhythm that is created with no effort to create a specific pattern of attacks or durations. Conversational speech, as illustrated in Figure 1, often uses unmeasured rhythm, as words are spoken to fulfill the practical necessities of communication rather than meeting an aesthetic standard.

Sounds that are created with rhythm in mind, as in reading a poem, giving a speech or performing a melody, are examples of measured rhythm. This can include sounds at a consistent interval, like the beeping of an alarm clock, or words deliberately spoken slowly to be more clearly heard.

A diagram showing each syllable of the chant `Say his name! George Floyd!` showing that the rhythmic interval of the first three syllables is doubled for the last two syllables.
Figure 2: A chant from a protest against police violence in Boston in 2020. Call and response chants tend to have strongly measured rhythms.

Rhythmic Intervals

When analyzing rhythm, theorists measure the intervals of time that elapse between sounds. This can be done in two different ways:

  • The interstimulus interval or ISI measures the amount of time between the end of one sound and the beginning of the next sound.
  • The interonset interval or IOI measures the amount of time between the attacks of two consecutive sounds, ignoring the sounds' durations.
A diagram two rhythms with notes at identical regular intervals, one with short durations and one with longer durations. The interonset interval is the same for both rhythms; the interstimulus interval is short for the rhythm with long durations, and longer for the rhythm with short durations.
Figure 3: Two rhythms that have identical interonset intervals. The sounds in the first rhythm have longer durations, causing the interstimulus intervals to be shorter.

Musicians often consider two patterns with the same IOI as having the same rhythm, even if the patterns' ISIs are different. For musical passages, changes in ISI are usually heard as affecting articulation, for example making a legato passage staccato, or vice versa.

Meter

In poetry, dance, and music, rhythms are often repeated in a regular, predictable pattern, creating an environment that can promote synchronization of other sounds or movements. This phenomenon is called meter.

A photograph of 11 musicians wearing dhotis and playing long drums hanging from shoulder straps in front of a jewelry store window.
Figure 4: Musicians playing chendas in a shopping center in Kerala, India. Percussion music tends to feature regular, repetitive rhythms.
(-Reji | CC BY-NC-ND-2.0)

Beat

When a rhythm is repeated, listeners usually perceive a consistent pulse, which musicians call a beat. A beat can be an audible part of the music being performed, or it can be an implied pulse created in the listener's mind as a result of other aural stimuli.

A diagram showing the text `I am sitting in the morning at the diner on the corner / I am waiting at the counter for the man to pour the coffee` with the syllables `sit-,` `morn-,` `din-,` `cor-,` `wait-,` `coun-,` `man` and `cof-` highlighted to show the implied beat on those syllables.
Figure 5: The first two lines of American singer/songwriter Suzanne Vega's 1982 song Tom's Diner. Though the song consists only of Vega's voice, the melody initially implies a strong, consistent beat.

Subdivision

In addition to perceiving a beat, listeners will usually hear or feel a smaller consistent rhythmic interval in a repeating pattern. This faster pulse is called a subdivision and takes two forms:

  • A simple subdivision is the division of the beat into two equal intervals.
  • A compound subdivision is the division of the beat into three equal intervals.
Figure 6: A demonstration of simple and compound beat patterns. Simple beats are subdivided into two equal segments, while compound beats are subdivided into three equal segments.

Measure

Just as a beat can be subdivided into shorter intervals, beats can be collected into larger regular groups. This is usually a result of phenomenal accents — sounds which have an increased intensity, such as a louder volume, longer duration or different pitch — played at regular intervals. However listeners can usually perceive implied accents resulting from melodic shape or articulation of adjacent notes, called metrical accents, which serve the same purpose.

A group of beats delineated by a metrical accent is called a measure or bar. In music, three types of measures are most common:

  • duple measures, which contain two beats,
  • triple measures, which contain three beats, and
  • quadruple measures, which contain four beats.
Figure 7: A demonstration of duple, triple and quadruple meters.

Theorists also use these terms to describe the meter of a passage of music; for example, a span of duple measures is said to be "in duple meter."

Isochrony

The most common types of meter in musical practice use isochronous beats: measures or larger sections of music where the beats are the same length, even if they are subdivided differently.

Figure 8: A sequence of isochronous beats.

Occasionally, composers will combine simple and compound beats containing subdivisions of the same length, sometimes in within a repeated pattern of measures. These are called non-isochronous beats, and a meter which uses non-isochronous beats in a regular pattern is considered to have a complex meter.

Figure 9: An example of a pattern with non-isochronous beats.

Rhythmic Relativity

Perception of beat and meter can vary from person to person, and what a composer or even performer intends to portray as a beat might be interpreted by a listener as a subdivision or measure.

For example, in a quadruple meter, the third beat of a measure is generally felt to have a secondary accent which is less energetic than beat one but more than beats two and four. Because of this, quadruple meter can be easily reinterpreted as duple meter with strong subdivisions: though it might be unambiguously notated one way or the other, how the music itself is felt is up to the listener.

A diagram showing three diagrammed beat patterns. In the first, two measures of quadruple meter are shown, each measure with a strong beat and three weak beats. The second is the same diagram, but the third beat in each measure shown as being stronger than the second and fourth beats, but not as strong as the first beat. The third diagram shows four measures of duple time.
Figure 10: In quadruple meter, the third beat of each measure is often heard as a secondary accent, which can easily reinterpreted as duple meter.

Hypermeter

Even if the beats and measures are clearly defined, meter can be felt on larger scales, across groups of measures or even larger sections of music. The arrangement of sections within a piece — and the particular relationships between them — is called form, but the point at which meter and form overlap, where small groups of measures portray rhythmic expectations similar to those within a meter, is called hypermeter.

Duration, Rhythm & Meter: Summary

  • Rhythm is the placement in time of a consecutive group of sounds.
    • The beginning of a sound is called its attack or onset.
    • The length of time between a sound beginning and ending is called its duration.
    • Sound has measured rhythm when it is made with a deliberate rhythm in mind; otherwise, we call it unmeasured rhythm.
    • The interval of time that passes between the end of one sound and the beginning of the next is called the interstimulus interval of ISI.
    • The interval of time that passes between the beginning of one sound and the begining of the next is called the interonset interval or IOI.
  • Meter is the system of regular pulses that emerge from the repetition of a rhythm or rhythms.
    • The regular pulse, audible or implied, that occurs when rhythms are continually repeated is called a beat.
    • Beats are often divided into subdivisions. A simple subdivision is a beat divded into two equal parts; a compound subdivision is a beat divided into three equal parts.
    • A measure is a collection of beats into a larger repeating structure, involving an accented beat followed by unaccented beats. Measures are classified by the number of beats they contain.
    • The meter of a section of music is determined by the types of measures (duple, triple, or quadruple) it contains and the type of beats (simple or compound) that it uses.
    • Isochronous beats are those which remain the same the length, regardless of how they are subdivided. Non-isochronous beats are consecutive beats which vary in length, often with a consistent subdivision.
    • A meter which combines simple and compound beats in a regular pattern is called a complex meter.
  • Hypermeter is the consideration of metrical structures larger than measures, which often overlaps with the concept of form.

Exercises