Compound metre

What it means

Time signatures whose beat divides into three equal parts are called compound. These include 6/8, 9/8, and 12/8, with two, three, and four beats per bar respectively. The beat is in every case the dotted quarter; the fraction, by contrast, names the thirds of this beat.

The counter-concept is the simple time signature, in which the beat divides into two parts — 2/4, 3/4, 4/4. The difference thus does not lie in the number of beats but in their subdivision. A six-eight bar and a two-four bar both have two beats; in one, each falls into three parts, in the other into two.

To be distinguished from this in turn are the irregular time signatures such as 5/8 or 7/8, whose groups are of unequal size.

In the notation

The beaming groups the small values into groups of three, one group per beat; from this the time signature is immediately recognizable in the notation. A full bar is filled by dotted values. Metronome markings refer to the dotted quarter — this is where the most common misunderstandings arise when setting the metronome.

Musical use

Compound time signatures carry dances such as the gigue and the tarantella, as well as barcarolles, pastorales, lullabies, and many folk songs. The rocking or rolling character arises from the continuous triple division, which avoids sharper accents. In fast movements, the same structure works propulsively. It is also widespread in popular music, there often as the shuffle feel of notated eighths.

It is distinguished from simple metre. Examples are 6/8, 9/8, and 12/8. In English it is called compound meter.

Performance practice

Count the beats, not the eighths, as soon as the tempo allows it. Keep the three notes of each group even — the middle one easily becomes too short and turns the group of three into a dotted figure. Accent the first beat of the bar distinctly, the remaining beats more lightly. And check, with every metronome marking, whether it refers to the dotted quarter before you set the tempo.