Interval vector

In musical set theory, an interval vector (also called an interval-class vector or ic vector) is an array that expresses the intervallic content of a pitch-class set. Often referred to as a PIC vector (or pitch-class interval vector), Michiel Schuijer suggests that APIC vector (or absolute pitch-class interval vector) is more accurate.

In twelve-tone equal temperament, an interval vector has six digits, with each digit representing the number of times an interval class appears in the set. Because interval classes are used, the interval vector for a given set remains the same, regardless of the set's permutation or vertical arrangement. The interval classes designated by each digit ascend from left to right. That is: