Rhythm is organized through meter, which groups beats into recurring patterns called measures. A time signature, placed at the beginning of a piece, indicates both how many beats are in each measure and which note value receives one beat. The 4/4 time signature, also called common time and often denoted by a C symbol, has four quarter-note beats per measure and is the most widely used meter in Western music.
Meters fall into two broad categories. In simple time, each beat divides naturally into two equal parts, as in 4/4 or 3/4. In compound time, each beat divides into three equal parts, and the top number is typically a multiple of three. A 6/8 meter has six eighth notes per measure grouped into two beats of three eighth notes each, producing the lilting feel of jigs, marches, and slow ballads. A 3/4 meter, commonly known as waltz time, has three quarter-note beats per measure with a strong-weak-weak pattern and is the signature meter of waltzes and minuets. Asymmetric or irregular meters such as 5/4, often grouped 3+2 or 2+3, create an uneven, driving feel heard in pieces like Dave Brubeck's Take Five and the Mission: Impossible theme.
Notes and rests are the building blocks of rhythm. From longest to shortest in 4/4 time, note values are whole (4 beats), half (2 beats), quarter (1 beat), eighth (½ beat), sixteenth (¼ beat), and thirty-second (⅛ beat), each half the duration of the previous one. A dotted note increases a note's duration by half its original value, so a dotted half note equals three beats and a dotted quarter note equals 1.5 beats. Rests mirror note values: a whole rest hanging from a line equals four beats, a half rest sitting on a line equals two beats, and quarter, eighth, and sixteenth rests equal one beat, half a beat, and a quarter beat respectively.
Several rhythmic techniques add complexity and interest. Syncopation emphasizes weak beats or offbeats, disrupting the expected pattern of accents and creating rhythmic tension and forward momentum; it is a defining feature of jazz, funk, reggae, and Latin music. A tuplet divides a beat into a number of equal parts different from the standard division; the most common is the triplet, which divides a beat into three equal parts in simple time, though quintuplets and septuplets also occur. A tie connects two notes of the same pitch, combining their durations into one sustained note, while a slur connects notes of different pitches to indicate they should be played smoothly. A hemiola is a rhythmic device in which two groups of three beats are reinterpreted as three groups of two beats, or vice versa, and is a common feature of Baroque and Latin music.