Time signature
A time signature (also known as meter signature,[1] metre signature,[2] and measure signature)[3] is a convention in Western music notation that specifies how many note values of a particular type are contained in each measure (bar). The time signature indicates the meter of a musical movement.
"Time (music)" redirects here. For other uses, see Half-time (music).
In a music score the time signature appears as two stacked numerals, such as 4
4 (spoken as four–four time), or a time symbol, such as 
(spoken as common time). It immediately follows the key signature (or if there is no key signature, the clef symbol). A mid-score time signature, usually immediately following a barline, indicates a change of meter.
Most time signatures are either simple (the note values are grouped in pairs, like 2
4, 3
4, and 4
4), or compound (grouped in threes, like 6
8, 9
8, and 12
8). Less-common signatures indicate complex, mixed, additive, and irrational meters.
Frequently used time signatures[edit]
Simple versus compound[edit]
Simple meters are those whose upper number is 2, 3, or 4, sometimes described as duple meter, triple meter, and quadruple meter respectively.
In compound meter, the note values specified by the bottom number are grouped into threes, and the upper number is a multiple of 3, such as 6, 9, or 12. The lower number is most commonly an 8 (an eighth-note or quaver): as in 9
8 or 12
8.
Other upper numbers correspond to irregular meters.
Signatures that do not fit the usual simple or compound categories are called complex, asymmetric, irregular, unusual, or odd—though these are broad terms, and usually a more specific description is any meter which combines both simple and compound beats.[7][8] The term odd meter, however, sometimes describes time signatures in which the upper number is simply odd rather than even, including 3
4 and 9
8.[9]
Irregular meters are common in some non-Western music, and in ancient Greek music such as the Delphic Hymns to Apollo, but the corresponding time signatures rarely appeared in formal written Western music until the 19th century. Early anomalous examples appeared in Spain between 1516 and 1520,[9] plus a small section in Handel's opera Orlando (1733).
The third movement of Frédéric Chopin's Piano Sonata No. 1 (1828) is an early, but by no means the earliest, example of 5
4 time in solo piano music. Anton Reicha's Fugue No. 20 from his Thirty-six Fugues, published in 1803, is also for piano and is in 5
8. The waltz-like second movement of Tchaikovsky's Pathétique Symphony (shown below), often described as a "limping waltz",[10] is a notable example of 5
4 time in orchestral music.
Examples from 20th-century classical music include:
In the Western popular music tradition, unusual time signatures occur as well, with progressive rock in particular making frequent use of them. The use of shifting meters in The Beatles' "Strawberry Fields Forever" and the use of quintuple meter in their "Within You, Without You" are well-known examples,[11] as is Radiohead's "Paranoid Android" (includes 7
8).[12]
Paul Desmond's jazz composition "Take Five", in 5
4 time, was one of a number of irregular-meter compositions that The Dave Brubeck Quartet played. They played other compositions in 11
4 ("Eleven Four"), 7
4 ("Unsquare Dance"), and 9
8 ("Blue Rondo à la Turk"), expressed as 2+2+2+3
8. "Blue Rondo à la Turk" is an example of a signature that, despite appearing merely compound triple, is actually more complex. Brubeck's title refers to the characteristic aksak meter of the Turkish karşılama dance.[13]
However, such time signatures are only unusual in most Western music. Traditional music of the Balkans uses such meters extensively. Bulgarian dances, for example, include forms with 5, 7, 9, 11, 13, 15, 22, 25 and other numbers of beats per measure. These rhythms are notated as additive rhythms based on simple units, usually 2, 3 and 4 beats, though the notation fails to describe the metric "time bending" taking place, or compound meters. See Additive meters below.
Some video samples are shown below.
corresponds to 9
8 meter;
corresponds to 3
4 meter;
corresponds to 6
8 meter;
corresponds to 2
4 meter.
Irregular bar[edit]
Irregular bars are a change in time signature normally for only one bar. Such a bar is most often a bar of 3/4, 5/4 or 2/4 in a 4/4 composition, or a bar of 4/4 in a 3/4 composition, or a bar of 5/8 in a 6/8 composition.
If a song is entirely in 4/4 a change to 3/4 will make the song feel like it has skipped a beat, the opposite is true for 5/4 where it feels like the song adds a beat. If a song changes to 2/4 is will make it feel like that bar is half as long as all the others[29][30]
Some popular examples include "Golden Brown" by The Stranglers (4/4 in a 3/4 composition), "I Love Rock 'n' Roll" originally by The Arrows (3/4 in a 4/4 composition), "Hey Ya!" by Outkast (2/4 in a 4/4 composition), and "Wuthering Heights" by Kate Bush (different kinds of irregular bars in a 4/4 composition).
Sources