So I think i have an understanding of how to harmonize the major scale to give me a major key. I take the notes of the scale and and using diatonics pick every-other note to the nth degree giving me my seven different chords. My question is can I apply the same principals to other scales, like the harmonic and melodic minor to get more exotic keys?
Like shown here?
https://www.guitarnoise.com/lesson/minor-progress/
You certainly can! And don't forget you can also keep stacking notes onto your triads, getting various types of sevenths, ninths, etc.,
Peace
OK, If you are harmonizing to make full blown 7th chords, it would look like this.
Major: Maj7,Min7,Min7,Maj7,7,Min7,Half Diminished 7th
Harmonic Minor: MinMaj7,HalfDiminished7th,Maj7#5,Min7,7,Maj7,Diminished 7th
Melodic Minor: MinMaj7,HalfDiminished7th,Maj7#5,7,7,Half Diminished 7th,Half Diminished 7th
Harmonic Major: Maj7, Half Diminished 7th, Min7, MinMaj7, 7, Maj7, Diminished 7
There are some great books on this subject.
Check out Gene Bertoncini and Mick Goodrick.