Butterfly chords are chords characterized by central symmetry, obtained through the mirror conjunction of two epsilon chords. Their name comes from the fact that their structure resembles two wings arranged around a common axis.
Structure
Butterfly chords derive from the combination of an epsilon chord with its mirror chord, placed in a complementary position beyond the octave. The result is a symmetrical structure in which the two sets of four notes face each other like two wings.
Since each epsilon chord extends up to a seventh, major or minor, the axis of symmetry is located between the seventh of the lower chord and the root of the upper chord. In this way, the overall structure does not coincide with a single epsilon, but with a broader construction based on the mirror reflection of two corresponding epsilons.
Main Configurations
The main configurations of butterfly chords are formed by two epsilon chords placed one below and one above, with the upper chord located an octave above the lower one. In the following table, both the lower and upper chords are indicated starting from C.
Between the top note of the lower chord and the bottom note of the upper chord, a central interval is thus created, serving as the axis of the structure.
The perfectly symmetrical configurations are as follows:
| Abbreviation | Lower chord | Upper chord | Structure |
|---|---|---|---|
| maj13 | C–D–G–B | C–E–A–B | 2 4 3 (2♭) 3 4 2 |
| maj13 | C–E–A–B | C–D–G–B | 3 4 2 (2♭) 2 4 3 |
| m13 | C–E♭–A♭–B♭ | C–D–G–B♭ | 3♭ 4 2 (2) 2 4 3♭ |
| m13 | C–D–G–B♭ | C–E♭–A♭–B♭ | 2 4 3♭ (2) 3♭ 4 2 |
| phryg | C–D♭–G–B♭ | C–E♭–A–B♭ | 2♭ 5♭ 3♭ (1) 3♭ 5♭ 2♭ |
The two maj13 and m13 configurations constitute the main pairs of major and minor type. The phryg configuration represents a further variant, based on a sharper and more concentrated symmetry.
Alongside these perfectly symmetrical forms, other combinations are also possible which, while maintaining the same intervallic framework, modify the quality of the intervals (major/minor). In this way, the principle of butterfly chords is not limited to the canonical configurations listed here, but opens up to a wider range of harmonic possibilities.
Related entries
Accordo epsilon
Vettore intervallare diatonico
Vettore delle classi diatoniche