Duple metre

Duple time (also called duple metre in British spelling) is a musical rhythm defined by having two main beats in each measure. This is shown by the top number in the time signature, which is usually 2, 4, or 8 (or multiples of these numbers). For example, time signatures like 2/4, 4/4, and 6/8 are common examples of duple time.

A simple duple rhythm divides each beat into two equal parts, while a compound duple rhythm divides each beat into three equal parts. Examples of these rhythms can be seen in drum patterns.

Although duple time requires the top number of the time signature to be divisible by 2, this does not always mean the music is in duple time. For instance, in the first movement of Maurice Ravel’s Piano Trio, the time signature is 8/8, but the beats are divided into 3+2+3 instead of 4+4. This creates a rhythm that is not duple time but instead an "odd time" pattern.

Duple time is often used in marches, especially in American music, because the clear strong and weak beats match the steady rhythm needed for marching. It is also common in styles like the polka, which has a distinct "oom-pah" rhythm. In contrast, the waltz uses triple time, which has a "oom-pah-pah" rhythm with three beats per measure.

Quadruple metre

Quadruple metre (or quadruple meter in US spelling, also called quadruple time) is a musical rhythm pattern that is divided into 4 beats per measure. This is shown by the number 4 in the top part of the time signature. The most common example is 4/4, also known as common time.

A simple quadruple drum pattern and a more complex quadruple drum pattern are shown below.

The time signature 4/4 is most frequently used in rock, blues, country, funk, and pop music. Although jazz music has become more varied since the release of Dave Brubeck's Time Out, most jazz songs and standards still use "common time," which is written as 4/4.