A tetrachord (TC) is four successive tones separated by three intervals.
The Names of Tetrachords
Tetrachords get described by the intervals between the tones.
Major: M2, M2, m2 → 221
Minor: M2, m2, M2 → 212
Upper Minor: m2, M2, M2 → 122
Whole Tone: M2, M2, M2 → 222
Harmonic: m2, m3, m2 → 131
Locrian: m2, M2, m2 → 121
