Pitch tells music where to go; rhythm tells it when. You can recognize many songs from their rhythm alone, clapped with no notes at all. Rhythm is also the part of music most tied to the body: walking, dancing, rowing, working and marching all move in time.

Beat and rhythm

The beat is the steady pulse underneath music, the thing you tap your foot to. It works like a clock's tick. Rhythm is the pattern of long and short sounds and silences laid over that pulse. In "Happy Birthday," the beat ticks evenly while the words fall into an uneven pattern: two quick notes on "happy," a longer one on "birth," and so on. Beat and rhythm are easy to confuse, but they are different. The beat is the grid; the rhythm is what is drawn on it.

Written music names durations by simple halving. A whole note lasts longest; a half note lasts half as long; a quarter note half of that; an eighth note half again. Silences have matching values, called rests.

Meter and the measure

Beats are rarely all equal. Listeners hear some as stronger and group the rest around them. Meter is the grouping of beats into a repeating pattern of strong and weak beats. Each group is called a measure or bar. The downbeat is the first beat of a measure, usually the strongest. Count "ONE two three four, ONE two three four" and you are feeling a meter of four.

Written music announces the meter with a time signature, two numbers stacked at the start. The top number of a time signature tells how many beats are in each measure, and the bottom number tells which note value gets one beat. Four four time, with four beats per measure, is so common that it is called common time; most rock, pop and hip hop live in it. A waltz is in three, with three beats per measure: ONE two three, ONE two three, the swaying pattern of Johann Strauss's "Blue Danube." Some meters divide each beat into three smaller parts instead of two, which gives a lilting, rocking feel. Many lullabies and jigs work this way.

Accent, syncopation and swing

Music gets much of its energy by playing with expectations about strong and weak beats. Syncopation is placing accents on weak beats or between beats, against the expected pattern. Ragtime, jazz, funk, reggae and much Latin American music depend on it. Reggae guitar often strikes on the offbeats, the "and" between the counts, which gives the style its springy lift. In jazz, swing divides each beat unevenly, long then short, rather than in two equal halves, so that a line of even notes takes on a loping, conversational gait.

Some music layers conflicting rhythms. A polyrhythm is two or more contrasting rhythmic patterns played at the same time, such as three evenly spaced beats against two in the same span. West African drum ensembles build rich textures this way, with each player holding a separate pattern and the whole emerging only from their combination. Cuban music organizes many of its patterns around the clave, a short, uneven rhythmic key that the whole band must respect. Traditions like these show that rhythm can be as complex as harmony, and they shaped much of the popular music of the Americas.

Tempo

Tempo is the speed of the beat, often measured in beats per minute. A resting heart beats around sixty to eighty times a minute; many pop songs fall between about ninety and one hundred thirty. Classical scores traditionally mark tempo with Italian words: largo for very slow, andante for a walking pace, allegro for fast and cheerful, presto for very fast. In 1815 Johann Maelzel patented a mechanical metronome, a ticking pendulum that could be set to an exact speed, and Beethoven was among the first composers to publish metronome markings for his works. Performers also bend tempo for expression, slowing into a climax or pushing ahead with excitement. This flexibility is called rubato, from the Italian for "robbed": time taken from one place and given back in another.

Worked example: two ways of counting

Stamp your feet twice and clap once, then rest, and repeat: stomp, stomp, clap, rest. You have just played the famous pattern of Queen's 1977 anthem "We Will Rock You." Count along and you will find four beats in each cycle, with the stomps on beats one and two, the clap on three and silence on four. The meter is four, the tempo is moderate, and the rhythm is so plain that a stadium of strangers can keep it together.

Now try "Take Five," recorded by the Dave Brubeck Quartet in 1959 and composed by its saxophonist Paul Desmond. Count along with the piano's repeated figure and you will keep coming up one beat "too many" if you count in four. The piece is in five: ONE two three FOUR five, often felt as a group of three plus a group of two. It became a hit despite that unusual meter, proving that a listener's body can learn a new pulse within a few bars. Comparing the two shows how much character comes from meter alone.