Topics covered on this page: Simple/compound time signatures – Relation of time signatures to time classification – Common time – Cut time – Alla breve – The tie – Rhythmic patterns – Syncopation
Musical compositions are metrically organized by a time signature. A time signature has two numbers placed on the staff with one above the other at the beginning of the composition.
The two types of time signatures that exist are ones for simple time and ones for compound time. Here is how to distinguish between simple and compound time:
If the upper number is 6, 9, 12, or 15, the time signature represents compound time. Any number other than these means that the signature represents simple time, including the number 3.
The top number in a simple time signature indicate the number of beats per measure. It also indicates if the meter is duple, triple, quadruple, or quintuple.
4 beats per measure, quadruple meter:
The upper number in a compound time signature does not indicate the number of beats per measure as in simple time. To find the number of beats per measure in this case, the upper number of a compound time signature is divided by three.
In both simple and compound time, the upper number indicates meter while the lower number indicates unit. In simple time, the lower number directly indicates the unit. In compound time, the lower number indicates the division of the unit.
In compound time, the upper number in a time signature is divided by 3 to give the meter, or beats per measure. In this example below there are 2 beats per measure. The lower number indicates the unit. So in 6/8, the unit is the 8th note:
Remember that in all compound time, a dotted note is used for the beats per measure.
A dotted note is always the unit in compound time. An un-dotted note is always the unit in simple time.
Time classification is expressed in terms like duple-simple, duple-compound, triple-simple, quadruple-simple, and quintuple-simple. The first portion of the classification refers to the number of beats per measure. The second portion refers to the classification being simple or compound time.
Duple = 2
Triple = 3
Quadruple = 4
Quintuple = 5
The simple chart below recaps all the common time signatures and how they are expressed using time classification:
4/4 = quadruple-simple
2/2 = duple-simple
2/4 = duple-simple
3/4 = triple-simple
6/8 = duple-compound
9/8 = triple-compound
12/8 = quadruple-compound
15/8 = quintuple-compound
Next section is Intervals