Rhythm & Meter

Compound Meter

Definition

A compound meter is one whose beats divide into three equal parts, such as 6/8, 9/8 and 12/8. Each beat is a dotted note, usually a dotted quarter worth three eighth notes.

In a compound meter, each beat divides into three equal parts instead of two. The beat is a dotted note, most often a dotted quarter, which holds three eighth notes. Compound meters have a rolling, lilting feel: think of a jig, a lullaby rocking back and forth, or a slow blues ballad in 12/8.

A treble-clef melody in 6/8, four bars. Bar 1: dotted quarter notes C5 and G4, counted 1 and 2. Bar 2: two groups of three beamed eighth notes, A4 B4 C5 and D5 C5 B4, counted 1 & a 2 & a. Bar 3: quarter C5, eighth B4, quarter A4, eighth B4, counted 1 a 2 a. Bar 4: a dotted half note C5. — Two beats per bar, each a dotted quarter. Bar 1 holds the beats themselves; bar 2 splits each beat into three eighth notes, beamed in threes; bar 3 uses the quarter-eighth pattern that gives compound meter its lilt; and the dotted half note in bar 4 fills the whole bar.

Reading a compound time signature

The top number of a common compound signature is 6, 9 or 12, and it counts the small notes, not the beats. To find the beats, divide the top number by three:

6/8: six eighth notes, two dotted-quarter beats (compound duple)
9/8: nine eighth notes, three dotted-quarter beats (compound triple)
12/8: twelve eighth notes, four dotted-quarter beats (compound quadruple)
6/4: six quarter notes, two dotted-half beats (compound duple)

In 6/8, 9/8 and 12/8, eighth notes are beamed in threes, one group per dotted-quarter beat. In 6/4, the dotted-half beat instead contains six eighth notes.

Three single bars in the treble clef. The 6/8 bar has two groups of three beamed eighth notes, numbered 1 and 2. The 9/8 bar has three groups, numbered 1 2 3. The 12/8 bar has three groups of three beamed eighth notes and a dotted quarter note, numbered 1 2 3 4. — Each bar is built from dotted-quarter beats, and each beat holds three beamed eighth notes. The beat numbers are printed under the first note of each beat: two beats in 6/8, three in 9/8 and four in 12/8, where the last beat is a single dotted quarter note.

Counting compound meter

There are two common ways to count 6/8:

Count the beats and their thirds: "1 & a 2 & a". This keeps the two big beats in front of you, and it works at any tempo.
Count every eighth note: "1 2 3 4 5 6", with the beats on 1 and 4. This is handy at slow tempos and when you are first learning a rhythm. The Write the Counts 4 worksheet counts this way.

Choose one system and stay with it inside a piece. Practice hearing two beats of three with Rhythm Dictation: Two Beats, Three Parts Each.

Compound or simple?

A compound meter can sound like a simple meter full of triplets, and in a sense it is: the beat splits into three in both cases. The difference is that in compound time the three-way split is the normal state of the music, so it needs no 3 over each group. The reverse also happens: a compound meter can borrow a two-way split, written as a duplet (see tuplet).

The most common confusion is 6/8 against 3/4. Both hold six eighth notes, but 6/8 groups them 3+3 (two beats) and 3/4 groups them 2+2+2 (three beats). Time Signatures II: Compound Time works through the whole family.

Common questions

Why is 6/8 counted in two and not in six?

Because its six eighth notes are grouped in two sets of three, and each set forms one beat, a dotted quarter. At slow tempos players often count all six, but the music still moves in two big beats.

Are triplets the same as compound meter?

Eighth-note triplets can divide a quarter-note beat into three, like the normal three-part division of a compound beat. But triplets can span other durations too. In compound meter, the ordinary three-part beat division needs no tuplet sign.