Simple and compound meter

A measure counts beats: two, three, four. But that is not the whole story. It still has to say which note value takes one beat, and what happens when that beat divides. Those two questions are what separate simple meter from compound meter.

The examples in this topic show numbers at the start of the staff. They are the time signature, the subject of the next topic. For now, look only at the notes.

The beat unit

The note value that stands for one beat of the measure is the beat unit. In theory any value will do, from the whole note to the sixty-fourth. In practice, Lacerda notes, the most used are the half note, the quarter and the eighth (Lacerda 1966, ch. VII).

Here is a melody in duple meter with the quarter note as the beat unit: each beat is a quarter.

Hear the passage

Simple meter: the beat divides in two

When the beat unit is a value without a dot, the meter is simple (Lacerda 1966, ch. VII). An undotted value divides naturally into two: a quarter into two eighths.

Hear the passage

Look at the second measure: the eighths are joined by beams in pairs, one pair for each beat. Count "one-and, two-and" as you listen.

Compound meter: the beat divides in three

When the beat unit is a dotted value, the meter is compound. And a dotted value, as the topic on dots showed, divides into three: a dotted quarter into three eighths.

Hear the passage

This is duple meter too, with two beats. But now each beat is a dotted quarter, and the eighths come in threes. The music takes on a different swing, the lilt of a barcarolle. Count "one-and-a, two-and-a", leaning on the first of each group.

Lacerda ties the two together by name: an undotted note is a simple value, a dotted one is a compound value, and the meter takes the name of its beat unit (Lacerda 1966, ch. VII).

The full table

Each meter, by its number of beats, can be simple or compound. Taking the quarter and the dotted quarter as beat units:

Beats	Simple: each beat holds	Eighths per measure	Compound: each beat holds	Eighths per measure
duple	2 eighths	4	3 eighths	6
triple	2 eighths	6	3 eighths	9
quadruple	2 eighths	8	3 eighths	12

Med calls a simple and a compound meter corresponding meters when they have the same number of beats and the same note as the beat unit, undotted in one and dotted in the other: simple duple on the quarter corresponds to compound duple on the dotted quarter (Med 1996, ch. XIX).

Beams show the beat

Look at the table again: simple triple and compound duple both hold six eighths per measure. On the page, the difference is in the beams joining the eighths.

Hear the passage

Hear the passage

The same six eighths. In the first, three beats of two eighths: the beams make three pairs. In the second, two beats of three eighths: the beams make two groups of three.

When you listen, the player plays both the same, because it does not mark accents. The difference is in the weight: in the first, sing leaning on the first of each pair; in the second, on the first of each three. Blatter describes exactly this ambiguity: six quick pulses can sound like two beats divided in three, which is compound, or like three beats divided in two, which is simple; and played slowly enough, they simply sound like six (Blatter 2007, part 1, art. 4).

One theory, and another

What this topic presents is the classification most widely taught in Portuguese: simple or compound according to whether the beat unit is undotted or dotted. Med points out it is not the only one. He calls it the "French" theory and presents, in another chapter, a "German" theory that classifies meters by their number of strong beats: a simple meter has a single strong beat, and a compound meter joins simple ones (Med 1996, ch. XXVIII).

In that other theory, quadruple meter is compound, because it adds two duple measures and has two strong beats, the exact opposite of the classification above. Med notes that the German theory changes nothing in performance, since it does not define the beat unit; it is another way of describing the same music. According to Med, the first is the one taught in France, Russia and Brazil, which is why it is the one used here.

What comes next

The numbers at the start of each staff sum up, in short, everything this topic explained: how many beats there are and which note value they are. How to read that pair of numbers, and why compound meters are written in a way that looks misleading at first, is the subject of the time signature.