Each meter can be described in terms of two categories:

One category tells us how beats are divided. In simple meter, beats are divided into two. In compound meter, beats are divided into three. The other category tells us how beats are grouped in measures. In duple meter, there are two beats per measure. In triple meter, there are three beats per measure. In quadruple meter, there are four beats per measure.

For example, in 4/4, there are four beats per measure (represented by quarter notes), and each beat is divided into two eighth notes. Therefore, 4/4 is a simple quadruple meter. You might count the rhythm below as "1-and-2-and-3-and-4-and." Notice that eighth notes are beamed in pairs. This means that each beat only contains two eighth notes.

The time signatures for simple and compound meters give different information. Simple-meter time signatures tell us how many beats there are per measure and what kind of note has the beat. On the other hand, compound-meter time signatures tell us how many beat divisions there are per measure and what kind of note has the beat division. For example, in 6/8, there are six beat divisions per measure and the eighth note gets the beat division. Because each beat divides into three and there are six total beat divisions, there are two beats per measure. Furthermore, three eighth notes per beat combine so that each beat is a dotted quarter note. For this reason, eighth notes are beamed in groups of three.

One other possibility for meter involves beats of unequal length. These are called asymmetric meters. The term "asymmetric" is used in place of simple or compound. The example below is representative of an asymmetric triple meter. Notice that beat 3 is longer than beats 1 and 2. Once again, the eighth notes are beamed according to beat lengths, so the three beats are a quarter note, a quarter note, and a dotted quarter note, respectively.