Distributional evenness

A scale is distributionally even (DE) if it has maximum variety 2; that is, each generic interval class ("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.