Compound time signatures introduce a different rhythmic feel compared to simple time. Instead of the main beat dividing into two, it divides into three, creating a characteristic flowing or lilting quality.
In compound time, the beat is a dotted note, which means it naturally divides into three equal subdivisions. This is the key difference from simple time, where the beat divides into two.
Common compound time signatures include 6/8, 9/8, and 12/8.
Key Idea:
Think of the main beat in compound time as having a "triplet" feel built into it.
Question 1: How many main beats are there in a bar of 9/8 time, and what note value represents one main beat?
Show Answer
There are three main beats (9 ÷ 3 = 3). Each main beat is a dotted crotchet.
Question 2: Is 3/8 a simple or compound time signature? Explain.
Show Answer
3/8 is a simple time signature (Simple Triple). The top number '3' indicates three beats, and the '8' means each beat is a quaver. The beat divides into two semiquavers. If it were compound, the top number would typically be 9 for three main beats (e.g., 9/16 for three dotted quaver beats).
Lesson Summary
- Compound Time: The main beat is a dotted note, dividing into three subdivisions.
- Common examples: 6/8 (two dotted crotchet beats), 9/8 (three dotted crotchet beats), 12/8 (four dotted crotchet beats).
- Top number of time signature is number of subdivisions; bottom number is subdivision note value (usually 8 for quaver).
- Number of main beats = Top number ÷ 3.
- Beaming in compound time groups notes to reflect the main dotted beat (often groups of three quavers).