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Time Signatures

Posted by Robert Thomas on 18th February 2011

Time Signatures are comprised of two numbers, one written above the other, and are used to indicate meter.1 They should be written boldly and be immediately recognizable. Time signatures are not fractions, and thus should not be separated by the short horizontal line that is normally used with a numerical fraction. On a single staff the numerals are placed within the limits of the outer staff lines. In chamber, orchestra, band, and other music for large ensembles, one will often see an enlarged signature serving several staves in order to make it easier to read the meter changes in the score. When time signatures appear in the context of prose, there should be no line between the numbers if they appear vertically (16th post 3/4 time signature).

In “simple time,” the top number indicates the number of beats in each measure while the bottom number indicates what note value receives one beat. In “compound time,” the top number indicates the division of the beat while the bottom number indicates the note value of the division. In compound time, therefore, the top number is the number of beats multiplied by three; in simple time, the top number may be any numeral. As the bottom number always refers to a note value, the only numerals that can be used are 1, 2, 4, 8, 16, 32, etc. (referring to the whole note, half note, quarter note, eighth note, sixteenth note, thirty-second note, etc.). It is important that the time signature used represent the musical pulse, not merely the content of the bar.2 A common mistake is to confuse25th post 3/2 time signature(simple triple) with25th post 6/4 time signature(compound duple), particularly when there is a temporary change of time with a value of the quarter note unchanged. For example, in the following the second bar is clearly in25th post 3/2 time signaturetime:25th post example 1
(25th post quarter note=25th post quarter noteover the meter change). If25th post 6/4 time signaturewere intended the correct notation would be:25th post example 2.

Time signatures are traditionally placed on each staff following the clef and key signature. If there is no key signature, the time signature should immediately follow the clef. When placed in the traditional position, the top number should occupy the top two spaces of the staff and the bottom number the bottom two spaces of the staff.

Contemporary practice has increased the number of time signature options available. Some of these include: larger time signatures may now be placed over several staves, the bottom number may be replaced by a note shape (e.g.,25th post noteshape time signature), meters may be combined to indicate either a fixed pattern of changing meters or a flexible alternation of simple and compound meters containing the same number of rhythmic units (e.g.,25th post alternate meterwould mean that the measures alternate, freely or strictly, between the compound meter16th post 6/8 time signatureand the simple meter16th post 3/4 time signature, compound time signatures consisting of more than one top number to indicate an unorthodox grouping of beats (e.g.,25th post additive meter), different meters occurring simultaneously (polymeter), mixed meters made of unequal units grouped within the measure (e.g.,25th post addition meter), and meters which include a fraction in the top number (e.g.,25th post fraction meter).

Time signatures should appear only when necessary — unlike clefs and key signatures they are not repeated at the beginning of every line of the score. When the meter changes over a system break, it is common practice to add a “cautionary” time signature at the end of the line preceding the change.


1 The25th post C signatureas a time signature means “common time,” i.e.16th post 4/4 time signaturetime. It has a long history, and until recently meant any kind of quadruple-time, simple or compound, such as16th post 4/4 time signature,25th post 4/2 time signature, or25th post 12/8 time signature, but16th post 4/4 time signatureis its only meaning in recent years. Similarly25th post Half Cmeans25th post 2/2 time signature. The use of16th post 4/4 time signaturefor25th post C signatureand of25th post 2/2 time signaturefor25th post Half Cis now fairly common.

2 For example,16th post 4/4 time signatureshould not be used when the rhythm is clearly25th post 2/2 time signature.

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