Meet 3-3, the "Harmonic Minor Trichord"

In a previous post we made a quick survey of the possible trichords according to Forte's classification. Trichord 3-3 (C-Db-E) and 3-3I (C-D#-E) is, I claim, the most interesting of all. This is because it's the only one that isn't found in the major scale except (a) the cluster of two semitones and (b) the augmented triad.

Here are some guitar-friendly voicings for 3-3; remember that octave placement isn't part of the definition of the trichord, so we can move the three pitches around to get different effects:

Here are the corresponding voicings for 3-3I, the set-theoretical inversion of 3-3. This is the same trichord from a Fortean perspective but I think the difference in sound is significant enough to make them worth separating:

Although they take a bit of getting used to, I think both are beautiful sounds, especially in the wide open voicings.

Among the common heptatonic scales 3-3 and 3-3I are found only within the Harmonic Minor, where they outline some of the most distinctive sounds in that scale. Each of them is found in two different places:

Harmonic Minor Scale 1 2 b3 4 5 b6 7
V 3-3 5 b6 7
VII 3-3 1 b3 7
bVI 3-3I 1 b6 7
VII 3-3I 2 b3 7

Both also belong to the octatonic diminished scales and can be used symmetrically to play those scales simply by moving any appropriate fingering up in minor thirds.