Meter signatures usually fall into two categories. Simple meters normally divide the beat into two equally faster notes. In contrast, compound meters normally divide the beat into three. It is the upper number of a meter signature that determines whether a meter is simple or compound. The top number of simple meters is usually 2, 3, or 4. The most commonly used compound meters have as their top number 6, 9 or 12. Meters with 6 as their top number are considered compound duple meters–they consist of two groups of three; meters with 9 as their top number are considered compound triple meters–three groups of three; and meters with 12 as their top number are considered compound quadruple meters–four groups of three. The following chart provides a clear idea of how the most commonly used simple and compound meters are grouped. The eighth notes are beamed according to the basic beat.
I especially want to draw your attention to compound duple (6/8) and simple triple (3/4). As you can see and hear, each of those two meters consist of six eighth notes, but sound very different. Note how differently they are grouped with beams. The 3/4 meter consists of three groups of two eighths; the 6/8 meter consists of two groups of three eighths. Each audio plays the excerpt twice.
Following are a few examples of compound meter and two alternate ways in which they might be counted:
Listen to the following melody in compound duple:
Look at the following rhythmic examples. The first is a generic rhythm (no meter), the second shows how the same rhythm would be grouped (beamed into basic beats) in 3/4, while the third example has the rhythm grouped in 6/8:
Following is a rhythm written without meter. On a separate sheet of paper, rewrite the rhythm in 3/4 meter and then in 9/8 meter beaming the notes together into basic beats where possible. Also add bar lines in the correct places. Keep in mind the 3/4 meter should be grouped into 3 groups of 2 eighth notes, and the 9/8 meter should be grouped into 3 groups of 3 eighth notes.
Triplets are used in compositions when the composer occasionally wants the beat subdivided into three instead of the usual two. If triplets are used extensively, it is wiser to write the music in a compound meter instead of a simple meter. Keep in mind that a group of notes marked as a triplet take up the same amount of time as two regular notes of the same value.
Listen to the triplets in the dramatic trumpet fanfare for the hymn “God of Our Fathers.”