The time signature (also known as "meter signature") is a notational convention used in Western musical notation to specify how many beats are in each measure and what note value constitutes one beat. Time signatures indicate meter, but do not necessarily determine it; the composer is free to write in a different meter than that indicated by the signature, so long as the measures contain the indicated number of beats.
Most time signatures comprise two numbers, one above the other. In text (as in this article), time signatures are written in the manner of a fraction: the example shown at right would be written 3/4 meaning that there are 3 quarter notes in each measure. Note that no line appears between the numbers when written in the music.
In a musical score, the time signature appears at the beginning of the piece, immediately following the key signature (or immediately following the clef if the piece is in C major or a modal subset). A mid-score time signature, usually immediately following a barline, indicates a change of meter.
Time signatures consist of two numbers, one on top of the other. The bottom number gives the type of note as a fraction of a whole note (a whole note is called a 'semibreve' in UK English) that is the "beat unit"; e.g., 4 on the bottom means quarter-note (crotchet) counts and 8 on the bottom mean eighth-note (quaver) counts. The top number specifies how many beats are in each measure. For instance, 2/4 means 2 quarter-note beats.
Time signatures can be "simple" or "compound".
The most common simple time signatures are 2/4, 3/4, and 4/4. The 4 at the bottom indicates that the beat unit is the quarter note or crotchet. For example, 3/4 means three quarter-note beats per measure.
The letter "C" is sometimes used for 4/4 time, also called "common time" or "imperfect time". The symbol is derived from a broken circle used in early music, where a full circle represented 3/4 time, called "perfect time". A "C" with a vertical line through it is used in place of 2/2, also known as "alla breve" or, colloquially, "cut time".
Unlike simple time, however, compound time uses a dotted note for the beat unit. Consequently, since it is impossible to indicate a dotted note by using a single, non-fractional number, the upper and lower numbers in compound time signatures do not represent the number of beats per bar and the beat unit, as they do in simple time.
For example, 12/8 time would be counted: One two three four five six seven eight nine ten eleven twelve (or alternatively, one and uh two and uh three and uh four and uh).
In compound time, the beat unit is always a dotted note value. The most common compound time signatures are 6/8, 9/8 and 12/8, denoting two, three and four dotted quarter note beats per bar.
|Simple time signatures|
|4/4 (quadruple)||common time: widely used in most forms of Western classical and popular music. Most common time signature in rock, blues, country, funk, and pop|
|2/2 (duple)||alla breve, cut time: used for marches and fast orchestral music. Frequently occurs in musical theater. Sometimes called "in 2".|
|4/2 (quadruple)||common in early music; rarer since 1600, although Brahms and other composers used it occasionally.|
|2/4 (duple)||used for polkas or marches|
|3/4 (triple)||used for waltzes, minuets, scherzi, and country & western ballads.|
|3/8 (triple)||also used for the above, but usually suggests higher tempo or shorter hypermeter.|
|Compound time signatures|
|6/8 (duple)||double jigs, polkas, fast obscure waltzes, marches and some rock music.|
|9/8 (triple)||"compound triple time", used in triple ("slip") jigs, otherwise occurring rarely (The Ride of the Valkyries is a familiar example)|
|12/8 (quadruple)||classical music; also common in slower blues, doo-wop and stripper music; also used more recently in rock music.|
Signatures which do not fit into the usual duple or triple categories are known as complex, asymmetric, or irregular, although these are broad terms, and usually a more specific description is appropriate. Most often these can be recognised by the upper number being 5, 7, or another, larger, prime number. The earliest examples of irregular signatures are found in instrumental music by Giovanni Valentini (1582–1649) and Anton Reicha (1770–1836), written in 5/4, 9/8, etc. Although these more complex meters were common in non-Western music, they were rarely used in formal written Western music until the late 19th century . The waltz-like second movement of Tchaikovsky's Pathétique Symphony (premiered in 1893) and the theme from Mission: Impossible, are two of the more familiar examples of 5/4. Examples from the 20th century include Holst's "Mars, the Bringer of War," (5/4) from the orchestral suite The Planets, and the ending of Stravinsky's Firebird (7/4).
Examples from the Western popular music tradition include Nick Drake's "River Man" (5/4), grunge band Soundgarden's "Outshined" (7/4), grunge band Alice In Chains' "Them Bones" (7/8 in the verse and 4/4 in the chorus), Canadian rock band April Wine's "Say Hello" (6/4), Radiohead's "15 Step" (5/4), "2+2=5" (7/8 then 4/4) and "Paranoid Android" (includes 7/4), metal band Metallica's "Blackened" (7/4 pre-verse, 6/4 verse and 4/4 chorus), Sufjan Stevens' "A Good Man is Hard to Find", and alternative rock band Incubus' "Make Yourself" (7/4 followed by two bars of 4/4). Progressive rock music made large use of unusual time as a defining characteristic; examples include "Money" (mostly 7/4, mixed with 4/4), from Pink Floyd, "Metropolis Pt. 1: The Miracle and the Sleeper" by Dream Theater. Beginning of instrumental section in 13/8, broken down as 6/8 + 7/8, and later as 4/4 + 5/8.
The jazz composition "Take Five", written in 5/4 time, was one of a number of irregular-meter experiments of The Dave Brubeck Quartet, which also produced compositions in 11/4 ("Eleven Four"), 7/4 ("Unsquare Dance"), and 9/8 ("Blue Rondo a la Turk"), expressed as (2+2+2+3)/8, this last being a good example of a work in a signature which, despite appearing merely compound triple, is actually more complex.
It should be pointed out that such time signatures are only considered "unusual" from a Western point of view. In contrast, for example, Bulgarian dances use such meters extensively, including 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 as compound meters, for example the Bulgarian Sedi Donka, consisting of 25 beats divided 7+7+11, where 7 is subdivided 3+2+2 and 11 is subdivided 2+2+3+2+2 or 4+3+4. See Variants below.
While time signatures usually express a regular pattern of beat stresses continuing through a piece (or at least a section), sometimes composers place a different time signature at the beginning of each bar, resulting in music with an extremely irregular rhythmic feel. In this case the time signatures are an aid to the performers, not an indication of meter. The Promenade from Mussorgsky's Pictures at an Exhibition is a good example:
Some pieces have no time signature, as there is no discernible rhythm. This is commonly known as free time. Sometimes one is provided (usually 4/4) so that the performer finds the piece easier to read, and simply has 'free time' written as a direction. Sometimes the word FREE is written downwards on the stave to indicate the piece is in free time. Erik Satie wrote many compositions which are ostensibly in free time, but actually follow an unstated and unchanging simple time signature throughout. Later composers have made more effective use of this device, writing music which is almost devoid of any discernible regularity of pulse.
If two time signatures alternate repeatedly, sometimes the two signatures will be placed together at the beginning of the piece or section, as in this example, the chorus from the song "America" from West Side Story: in this case, it alternates between 6/8 (in two) in the first measure of each pair and 3/4 (in three) in the second measure.
To indicate more complex patterns of stresses, such as additive rhythms, more complex time signatures can be used. For example, the signature : which can be written 3+2+3/8, means that the first of a group of three eighth notes (quavers) is to be stressed, then the first of a group of two, then first of a group of three again. The stress pattern is usually counted as one-two-three-one-two-one-two-three. This kind of time signature is commonly used to notate folk and non-Western types of music. In classical music, Béla Bartók and Olivier Messiaen have used such time signatures in their works.
Romanian musicologist Constantin Brăiloiu had a special interest in compound time signatures, developed while studying the traditional music of certain regions in his country. While investigating the origins of such unusual meters, he learned that they were even more characteristic of the traditional music of neighboring peoples (e.g. the Bulgarians). He suggested that such timings can be regarded as compounds of simple two-beat and three-beat meters, where an accent falls on every first beat, even though, for example in Bulgarian music, beat lengths of 1, 2, 3, 4 are used in the metric description. In addition, when focusing only on the stressed beats, the simple time signatures themselves will count as beats in the compound time. There will be two kinds of beats with the resulting compound time, of which the simple "three-beat" will be fairly longer than the "two-beat".
Folk music may make use of metric time bends, so that the proportions of the performed metric beat time lengths differ from the exact proportions indicated by the metric. Depending on playing style of the same meter, the time bend can vary from non-existent to considerable; in the latter case, some musicologists may want to assign a different meter. For example, the Bulgarian tune Eleno Mome is written as 7=2+2+1+2, 13=4+4+2+3, 12=3+4+2+3, but an actual performance (e.g. Smithsonian Eleno Mome) may be closer to 4+4+2+3.5. The Macedonian 3+2+2+3+2 meter is even more complicated, with heavier time bends, and the use of quadruples on the threes; the metric beat time proportions may vary with the speed the tune is being played. In Western classical music, metric time bend is used in the performance of the Viennese Waltz. Most Western music uses metric ratios of 2:1, 3:1, or 4:1 (two-, three- or four-beat time signatures) — in other words, integer ratios which determine all beats to be of equal time length; so relative to that, 3:2 and 4:3 ratios corresponds to a very distinctive metric rhythm profiles — complex accentuation is used in Western music, but not as a part of the metric accentuation, instead viewed as syncopation.
Brăiloiu borrowed a term from Turkish medieval music theory: aksak (Turkish for "crippled"). Such compound time signatures fall under the aksak rhythm category that he introduced along with a couple more that should describe the rhythm figures in traditional music. (Aksak is sometimes spelled as aksaac, because there isn't an exact transliteration from medieval Turkish into Latin alphabet.) The term Brăiloiu revived had a moderate success worldwide, but in Eastern Europe it is still frequently used. However, aksak rhythm figures are to be found not only in a few European countries, but on all continents, featuring various combinations of the "two" and "three" sequences. Yet the longest were found in Bulgaria; the shortest aksak rhythm figures would be the five-beat timing, comprising a "two" and a "three" (which can be also ordered as "three" followed by the "two").
Music educator Carl Orff proposed replacing the lower number of the time signature with the actual note value, as shown at right. This system eliminates the need for compound time signatures (described above), which are confusing to beginners. While this notation has not been adopted by music publishers generally (except in Orff's own compositions), it is used extensively in music education textbooks. Similarly, American composers George Crumb and Joseph Schwantner, among others, have used this system in many of their works.
Another possibility is to extend the barline where a time change is to take place above the top instrument's line in a score and to write the time signature there, and there only, saving the ink and effort that would have been spent writing it in each instrument's staff. Henryk Górecki's Beatus Vir is an example of this. Alternatively, music in a large score sometimes has time signatures written as very long, thin numbers covering the whole height of the score rather than replicating it on each staff; this is an aid to the conductor, who can see signature changes more easily.
These are time signatures which have a denominator which is not a power of two (1, 2, 4, 8, 16, 32, etc.). These are used to express the division of a whole note (semibreve) into equal parts just as ordinary signatures do. For example, where 4/4 implies a bar construction of four quarter-parts of a whole note (i.e., four quarter notes), 4/3 implies a bar construction of four third-parts of it. These signatures are only of utility when juxtaposed with other signatures with varying denominators; a piece written entirely in 4/3, say, could be more legibly written out in 4/4.
It is arguable whether the use of these signatures makes metric relationships clearer or more obscure to the musician; it is always possible to write a passage using non-"irrational" signatures by specifying a relationship between some note length in the previous bar and some other in the succeeding one. Sometimes, successive metric relationships between bars are so convoluted that the pure use of irrational signatures would quickly render the notation extremely hard to penetrate. Good examples, written entirely in conventional signatures with the aid of between-bar specified metric relationships, occur a number of times in John Adams' opera Nixon in China (1987), where the sole use of "irrational" signatures would quickly produce massive numerators and denominators.
Historically, this device has been prefigured wherever composers have written tuplets; for example, a 2/4 bar consisting of 3 triplet crotchets could arguably more sensibly be written as a bar of 3/6. Henry Cowell's piano piece "Fabric" (1920) throughout employs separate divisions of the bar (anything from 1 to 9) for the three contrapuntal parts, using a scheme of shaped noteheads to make the differences visually clear, but the pioneering of these signatures is largely due to Brian Ferneyhough. Thomas Adès has also made extensive use of them, for example in his piano work "Traced Overhead" (1996), the second movement of which contains, among more conventional meters, bars in such signatures as 2/6, 9/14 and 5/24. His "Piano Quintet" (2000) makes such extensive use of these, including different lines juxtaposed with varying meters, that an alternate form of notation is not immediately obvious, or arguably desirable. A gradual process of diffusion into less rarefied musical circles seems to be underway, hence for example, John Pickard's work "Eden", commissioned for the 2006 finals of the National Brass Band Championships of Great Britain, which contains bars of 3/10.
Notationally, rather than using Cowell's elaborate series of notehead shapes, the same convention has been invoked as when normal tuplets are written; for example, one beat in 4/5 is written as a normal quarter note, four quarter notes complete the bar, but the whole bar lasts only 4/5 of a reference whole note, and a beat 1/5 of one (or 4/5 of a normal quarter note). This is notated in exactly the same way that one would write if one were writing the first four quarter notes of five quintuplet quarter notes.
The term "irrational" is not being used here in its mathematical sense: an irrational number is one that cannot be written as a ratio of whole numbers, which all these signatures obviously are. Nevertheless, the term appears to be established now, although at least one such piece with a truly irrational signature already exists: one of Conlon Nancarrow's "Studies for Player Piano" contains a canon where one part is augmented in the ratio √42:1 (6.4807407:1)
At other times, the choice of beat unit (the bottom number of a time signature) note can give subtle hints as to the character of the music: for example, time signatures with a longer beat unit (such as 3/2) can be used for pieces in a quick tempo to convey a sense of the time flying by. This may be counter-intuitive, but in the Baroque and Classical periods, typically meters with long note values (such as 3/2) were fast tempos, while slow movements were typically written with the eighth note as the beat.
Similarly, a piece in 2/4 can often sound as if it is in 4/4 (or vice versa) and a piece in 3/4 can sound as if it is in 6 or 12 compound time, particularly if the former is played quickly or the latter slowly. The distinction may be a matter of notation.
In the 15th and 16th centuries, a period in which mensural notation was used, there were four basic time signatures, which determined the proportion between the two main units of rhythm. There were no measures or bar lines in music of this period; these signs, the ancestors of modern time signatures, indicate the ratio of duration between different note values. The relation between the breve and the semibreve was called tempus, and the relation between the semibreve and the minim was called prolatio. Unlike modern notation, the duration ratios between these different values was not always 2:1; it could be either 2:1 or 3:1, and that is what these mensural signatures indicated. A ratio of 3:1 was called complete, perhaps a reference to the Trinity, and a ratio of 2:1 was called incomplete.
A circle used as a time signature indicated tempus perfectum (a circle being a symbol of completeness), while an incomplete circle, resembling a letter C, indicated tempus imperfectum. Assuming the breve to be a beat, this corresponds to the modern concepts of triple meter and duple meter, respectively. In either case, a dot in the center indicated prolatio perfecta while the absence of such a dot indicated prolatio imperfecta, corresponding to simple meter and compound meter.
A rough equivalence of these signs to modern meters would be:
N.B. in modern compound meters the beat is a dotted note value, such as a dotted quarter, because the ratios of the modern note value hierarchy are always 2:1. Dotted notes were never used in this way in the mensural period; the main beat unit was always a simple (undotted) note value.
Often the ratio was expressed as two numbers, one above the other, looking similar to a modern time signature, although it could have values such as 4/3, which a time signature could not.
There is still controversy regarding the meaning of some proportional signs, and they may not have been used consistently from one place or century to another. In addition, certain composers delighted in creating "puzzle" compositions which were intentionally difficult to decipher.
In particular, when the sign was encountered, the tactus (beat) changed from the usual semibreve to the breve, a circumstance called alla breve. This term has been sustained to the present day, and although now it means the beat is a minim (half note), in contradiction to the literal meaning of the phrase, it still indicates that the beat has changed to a longer note value.
In the 17th century, additional signs such as also indicated proportions like this.