Well, through the work I’ve been doing with fretful (Fretful.io (fretboard visualizer) - Alpha release) I finally understood what modes are for and consequently how to derive any chord from any scale. And specially why they are so useful for improvising! This was a seriously mind exploding “ah hah!” moment for me.
So, take C major scale and its modes for instance:
C Ionian
Intervals: P1, M2, M3, P4, P5, M6, M7, P8
Ok, that’s a C major / C major 7
D Dorian
Intervals: P1, M2, m3, P4, P5, M6, m7, P8
Ok, that’s a D minor / D minor 7
E Phrygian
Intervals: P1, m2, m3, P4, P5, m6, m7, P8
Ok, that’s a E minor / E minor 7
F Lydian
Intervals: P1, M2, M3, A4, P5, M6, M7, P8
Ok, that’s a F major / F major 7
G Mixolydian
Intervals: P1, M2, M3, P4, P5, M6, m7, P8
Ok, that’s a G major / G dominant 7
A Aeolian (minor)
Intervals: P1, M2, m3, P4, P5, m6, m7, P8
Ok, that’s a A minor / A minor 7
B Locrian
Intervals: P1, m2, m3, P4, d5, m6, m7, P8
Ok, that’s a B diminished / B minor 7th flat 5
Still to figure out, why the hell are there only major and minor keys.