Simple and Compound Meters

In the previous lesson we saw that the time signature shows how many beats each measure has. But there is a second level: what happens inside each beat. That is where meters split into simple and compound.

01The beat subdivides

The beat is not indivisible. You can "break" it into smaller, equal parts. The way it subdivides is exactly what separates the two families of meters. Either into two parts, or into three.

How the beat "breaks"

Simple meter

↓ subdivides

into 2 equal parts

Compound meter

↓ subdivides

into 3 equal parts

That small difference, two or three, changes the entire feel of the rhythm.

02Simple meters

In simple meters each beat subdivides into two. These are the meters we have already seen: 2/4, 3/4 and 4/4. The bottom number stands for a quarter, which naturally subdivides into two eighths.

Every meter you have met so far has been simple.

03Compound meters

In compound meters each beat subdivides into three parts. The most common compound meter is 6/8.

In 6/8 the top number says each measure holds 6 eighths. But you don't feel them as 6 separate beats. They group into two sets of three, and each set of three is one beat.

6/8: six eighths, two beats

So you feel 6/8 as two beats, each subdividing into three. The beat you feel is a dotted note, lasting three eighths.

The other compound meters are read the same way. 9/8 has three groups of three, so three beats, and 12/8 four groups of three, so four beats. A simple rule helps you recognize them: when the top number is 6, 9 or 12, the meter is compound.

04Same beats, different feel

But why write 6/8 and not simply 2/4? Because they are not the same thing. 2/4 and 6/8 both have two beats. The difference is in what happens inside the beat.

2/4 and 6/8: same beats, different subdivision

2/4 · Simple · Two beats

2 beats
each subdivides into 2 a straight, square feel

6/8 · Compound · Two beats

2 beats
each subdivides into 3 a rolling feel, in threes

In 2/4 the beat subdivides into two and you get a straight, square feel. In 6/8 it subdivides into three and you get a rolling feel, as if it runs in threes. Many pieces ride exactly on that 6/8 feel.