Time signature

The time signature is used in Western rhythmic notation[?] to specify the basic rhythm of a piece of music, also known as its meter. A time signature is a fraction. In "simple" time signatures, the denominator indicates which note is the beat. If the denominator is 2, the half note is one beat; if the denominator is 4, the quarter note is one beat; and so on. The numerator indicates the number of beats in each measure. Examples of simple time signatures include "4/4" ("common time"), "2/2" ("cut time"), "3/4", "5/4", "2/4", and so on.

Time signatures where the numerator is a multiple of three (excluding the number 3 itself) are typically "compound" time signatures. In a compound signature, the denominator does not specify which note is the beat. Instead, each beat is divided into three sub-beats, and the denominator of the time signature determines what sort of note makes up a sub-beat. In "6/8" time, the sub-beats are eighth notes, and three of them make up a single beat. This means that the beat is a dotted-quarter note, and there are two beats in a measure. Other examples of compound time signatures include "9/8", "6/16", and so on. It is not uncommon to for listeners to confuse a 3/4 (simple) time signature with a 6/8 (compound) signature, if the former is played rapidly, or the latter is played slowly.

In modern Western Music[?], in styles such as serialism and minimalism, the time signature is often avoided entirely, along with the key signature. In other cultures, time is maintained not by a defined notation, but by a drum or other percussion instrument. Examples of this can be found in Indian classical music (see Indian music) and gamelan music, both of which often rely on oral tradition to pass down popular songs, rather than notation, as in Western classical music (see Western music).

Some standard time signatures in Western music are

• 4/4 or C -- common time
• 1/1 -- used very rarely, several times by Edward Elgar in several of his studies.
• 2/2 or ¢ -- cut time, used for marches
• 2/4 -- used for polkas or marches
• 3/4 -- used for waltzes, minuets and scherzi
• 6/8 -- used for fast waltzes or marches
• 5/4 -- used for Dave Brubeck's "Take Five" and the original versions of the theme from Mission: Impossible¹. It is also used in classical music by Gustav Holst in "Mars" from The Planets. 5/4 is usually grouped as 3+2 or 2+3.
• 7/4 -- used for "Money" by Pink Floyd, numerous Genesis songs and "The Unsquare Dance" by Dave Brubeck.

Other meters are sometimes encountered as well. Dave Brubeck in particular made use of unusual time signatures in his music.

See also: Musical notation

¹ The theme songs from the M:I feature films (1996 and 2000) use 4/4 by repeating the first three beats of the bass line twice, holding melody notes during that period, and halving each note's duration.