The gap between a bright chord and a dark one is a single semitone. Lower the middle note of the three and the brightness flips.
Chapter five showed that bright and dark come from spacing. The same thing happens inside a chord — and only one note moves.
- CC (bright)
- CmCm (dark)
The outer notes, C and G, are the same in both. The middle one is E in C and E♭ in Cm. One semitone, and that much difference in feeling.
The third note counting up from the bottom of a triad. It decides bright or dark, which makes it the note that gives a chord its character.
See which key actually moves
One key moved, and only to its neighbour. Knowing that a difference this small separates "a bright song" from "an aching one" makes chord symbols suddenly worth reading.
- Built major (C, F, G)
C | F | G | C
- Built minor (Cm, Fm, G)
Cm | Fm | G | Cm
Generate over the minor progression. Same note count, different feeling — compare it against what you made in part one.
Generate over the minor progressionThe middle note decides bright or dark. Lower it and you have minor; put it back and you have major. Nothing else changes.