# Why is meter divided into simple and compound types?

From what I understand,

• Simple Meter -- divisible by twos
• Compound Meter -- divisible by threes

Why do we choose 2 and 3? Why not n divisions?

The difference between a simple meter and compound meter greatly affects the feel of the piece and the differences are bigger than you think. There are other types out there, but let's correct some definitions first. A simple meter is not defined by being divisible 2s and a compound meter is not defined by being divisible by 3s. It's much more about the subdivisions

A simple meter is a meter that has the beat assigned to a simple note duration represented by the lower number of a time signature. The subdivision of the beat of a simple meter are in two. So in 2/4, 3/4, and 4/4 you would count the following way:

``````X: 1
M: 2/4
K: Cmaj
L: 1/8
"1"G"+"G "2"G"+"G|
``````
``````X: 1
M: 3/4
K: Cmaj
L: 1/8
"1"G"+"G "2"G"+"G "3"G"+"G|
``````
``````X: 1
M: 4/4
K: Cmaj
L: 1/8
"1"G"+"G "2"G"+"G "3"G"+"G "4"G"+"G|
``````

A compound meter is a meter that has the beat assigned to 3 of the note duration represented by the lower number of a time signature (so for 6/8 the beat is a dotted quarter note which is 3 eighth notes). The subdivision of the beat of a compound meter are in three. So in 6/8, 9/8, and 12/8 you would count the following way:

``````X: 1
M: 6/8
K: Cmaj
L: 1/8
"1"G"+"G"a"G "2"G"+"G"a"G|
``````
``````X: 1
M: 9/8
K: Cmaj
L: 1/8
"1"G"+"G"a"G "2"G"+"G"a"G "3"G"+"G"a"G|
``````
``````X: 1
M: 12/8
K: Cmaj
L: 1/8
"1"G"+"G"a"G "2"G"+"G"a"G "3"G"+"G"a"G "4"G"+"G"a"G|
``````

You'll notice that both 6/8 and 3/4 contain the same number of eight notes as does 12/8 and 4/4, but the feel of the two are very different. If it helps you can think of compound meter as having a "triplet feel".

Now, let's get to the why not n. There are plenty of time signatures that are not simple or compound, but typically the are grouped in smaller subdivisions of 2 or 3 which is key. These are typically known as odd meters. For example 7/8 can be grouped as 1 group of 3 and two groups of 2. This helps stress accents and define the feel of the meter. Subdivisions of 2 and 3 are seen as the building blocks of any meter and bigger groups of them are just seen as combinations of the 2 and 3 subdivisions.