Simple time signatures
Simple time signatures have 2, 3, 4 on top and each beat can be broken into groups of 2.
Compound time signatures
Compound time signatures have 6, 9, 12 on top. Examples:
- 6/8
- 9/8
- 12/8
They are grouped into 3’s in terms of their feel or metric stress. That is, 6/8 has a strong grouping of 3 (emphasis on 1) and a weak grouping of 3 (emphasis on 4).
Irregular time signatures
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Other cases
3/4 vs 3/8
There’s not really much of a difference between these two time signatures - one may expect 3/8 to be like 6/8 but with a singular grouping of 3 notes. This isn’t the case. It’s instead like 3/4: do not think of these notes as a grouping.
It’s slightly more common to see 3/8 used in place of 3/4 at faster tempos.
3/4 vs 6/8
6/8 is TWO groups of THREE 8th notes.
3/4 is THREE groups of TWO 8th notes.
6/8 emphasizes beats 1 and 4.
3/4 emphasizes beat 1.
6/8 feels like a pendulum swinging.
3/4 feels ike a waltz.
A slow 6/8 can feel like a 3/4.
A fast 3/4 can feel like a 6/8.
Swung 3/4 vs. 9/8
9/8 can be thought of as the same as a swung 3/4.
9/8
In contemporary music, it is more common to think of 9/8 as a irregular time signature. Examples:
- 2 + 2 + 2 + 3
- 3 + 4 + 2