# Distributional Evenness

A scale is **distributionally even (DE)** if it has maximum variety 2; that is, each class of interval ("seconds", "thirds", and so on) contains **no more than** two specific intervals.

In practice, such scales are often referred to as "MOS" scales, but some consider this usage to be technically incorrect because a MOS as defined by Erv Wilson was to have **exactly** two specific intervals for each class other than multiples of the octave. When Wilson discovered MOS scales and found numerous examples, DE scales with period a fraction of an octave such as pajara, augmented, diminished, etc. were not among them.