Music Theory for the 21st-Century Classroom

Meter describes the number of beats in a measure (also know as a “bar”) and how the beats are normally divided.

Beat is "[t]he basic pulse underlying measured music and thus the unit by which musical time is reckoned..." according to Barry Kernfeld in The New Grove Dictionary of Jazz, 2nd edition. Pulse and beat are synonymous.

Tempo refers to the speed of the beat or pulse. Tempo can be referred to in beats per minute (bpm), such as 60bpm (where the rate of the beat would be equal to a second), or, in classical music, with terms like Allegro, Andante, and Adagio, sometimes in combinations with "M.M." for Maelzel’s Metronome.

Meters with two beats in a bar are described as duple. If there are three beats in a bar, the meter is described as triple, and if there are four beats in a bar, the meter is described as quadruple.

If the beats are normally divided into two parts, the meter is described as simple. If the beats are normally divided into three parts, the meter is described as compound.

The time signature \(\begin{smallmatrix}2\\8\end{smallmatrix}\) is “simple duple meter.” The time signature \(\begin{smallmatrix}3\\2\end{smallmatrix}\) is “simple triple meter.” Finally, \(\begin{smallmatrix}4\\4\end{smallmatrix}\) is “simple quadruple meter.”

When describing meter, we say how the beat is divided before the number of beats in the measure.

With compound meters the bottom number specifies the division of the beat. The beat value is a dotted note. We say \(\begin{smallmatrix}6\\16\end{smallmatrix}\) is “compound duple meter” because it has two beats. The time signature \(\begin{smallmatrix}6\\8\end{smallmatrix}\) is also compound duple. Compound time signatures have a top number greater than four that is divisible by 3 (6, 9, 12).

The following table summarizes meter and time signatures.