These sets are analogous to chords in traditional theory, but are really any group of notes.
Chords are nonlinear pc sets.
In set theory this chord is identified as 056. This provides a way of identifying and discussing the use of this chord and other unconventional chords. It also embraces all traditional chords under the same theory. Numbers are also used to represent intervals in semitones. A minor third, for example, is 3 semitones, or just 3.