In diatonic set theory, the deep scale property is the quality of pitch class collections or scales containing each interval class a unique number of times. Examples include the diatonic scale (including major, natural minor, and the modes) (Johnson, 2003, p. 41).
The common tone theorem describes that scales possessing the deep scale property share a different number of common tones for every different transposition of the scale, suggesting an explanation for the use and usefulness of the diatonic collection (Johnson, 2003, p. 42).
References
Deep scale property Wikipedia(Text) CC BY-SA