While a measure is usually the size of a musical motif (but often also of a fragment or phrase), a metric group is the size of a musical proposition, and a metric row is the size of a musical period. The terms musical proposition and metrical group should not be confused, nor should the terms musical period and metrical row. The proposal is one part of the (particular) melody itself. It encompasses both its rhythm and its intonation, whereas the metrical group encompasses only the number of measure times included within the boundaries of the musical proposal and their grouping (or accentuation) by simple and complex measures without regard to its particular rhythm and its particular intonation. For example, musical propositions with a variety of rhythmic and tonal content can be accommodated within the boundaries of a four-bar hexameter group.

In our music download there is a very wide variety of metrical groups and metrical ranks. Their classification is a difficult and delicate task.

Depending on the number of n,a complex bars that go into their composition, metrical groups can be two-stop and, three-stop and, four-stop and, five-stop, similar to two-stop, three-stop, four-stop and five-stop bars. And depending on how the compound bars (joints) are arranged and grouped in the metric group, it can be equal and unequal.

Metric ranks are also of different types according to the number and type of metric groups that form them. They are bicollinear when they are formed by two metric groups, tricollinear when they are formed by three groups, four-collinear when they are formed by four, and five-collinear when they are formed by five. Furthermore, they can be equal-cored and unequal-cored according to whether they are formed from equal or unequal metric groups.