# Time Signatures

The symbol of a time signature indicates the meter of a piece. In modern notation, it is typically represented by two numbers vertically aligned. The bottom number (denominator) stands for the unit of measurement, that is, the note value representing the beat-unit; the top number (numerator) indicates the metrical unit as the number of units per measure.  To sum up, a time signature expresses the number of beats in a measure versus the type of beat-unit.

In a time signature, the number as denominator represents one specific note-value as the beat-unit. And the numbers that can be used are limited to 1, 2, 4, 8, 16, 32, 64. Why these and not any others? Because they represent the proportional relations between all note values. Since the whole note is the largest and therefore the referential value it gets to be represented by 1. The value of one whole note equals to two half notes, hence 2 representing the half-note, four quarter notes are equal to the duration of one whole-note, then the quarter-note is represented by 4, and so on.

Examples of Time Signatures - What does 4 4 time mean?

A time signature  4 / 4 means that:
• the beat-unit equals to a quarter note (denominator)
• each measure has a time-length equal to four quarter notes (numerator).

A time signature  3 / 4 means that:
• the beat-unit equals to a quarter note (denominator)
• each measure has a length equal to the combined duration of three quarter notes (numerator).

A time signature 3 / 2 means that:
• the beat-unit equals to a half-note (denominator)
• each measure has a time-length equal to three half-notes (numerator).

A time signature 8 / 8 means that:
• the beat-unit equals to an eighth note (denominator)
• each measure has a total time-length equal to eight eighth-notes (numerator).

Time Signature Change

A time signature is graphically positioned in the beginning of a movement at the right of the clef and key signature. During the course of a composition, to indicate a change in meter, the new meter appears at the right side that closes the previous measure.

Alla Breve

Some specific time signatures may be written differently with icons without the use of numerical ratios, as C instead of 4/4, and C in the place of 2/2 (also called alla breve, also known as cut-time or half-time).