Not only for jazz lovers. I use them a lot, too. I like music theory in general. May I talk a little about it? I will just stick to the main aspects, which I think are pretty important. I hope, I'm not talking shit. I know, this will be just a little part of the whole music theory. So let's start.
The main scale is the major scale, everything comes from it. If you build triads over each of the 7 notes of the major scale, then you get 3 MAJOR CHORDS (I, IV and V), 3 MINOR CHORDS (II, III and VI) and 1 DIMINISHED CHORD (VII). But just using those triad chords is a little boring, so I suggest to use chord extensions as well. And now, that's interesting. We just take a look on the chord extensions, which are notes from the major scale.
For the 3 MAJOR CHORDS, the best extensions in my opinion, are the major second, the major sixth and the major seventh as natural chord extensions, with the exception of the V, which has a minor seventh. They usually don't need to just act as suspended notes. They make your boring triad chords sound much more interesting and beautiful!
For the 3 MINOR CHORDS, the best extensions in my opinion, are the perfect fourth, the minor seventh and the major second, with the exception of the III. There would be a minor second and this does only sound good when acting as a suspended note.
For the DIMINISHED CHORD, I don't know, which extension would sound best, because I usually don't use diminished chords in my songs.
So here we go, these were my thoughts about music theory. I hope you could understand, what I was talking about and I hope you liked it.
S3C
some pedantic nitpick/extensions (pun intended) to this newspost:
- the diatonic major scale is a good premise, but in entirety of the 12 note western system, it's not where everything comes from. As an example, rotate to the sixth mode (Aeolian), sharp the 7th, and you've got harmonic Minor. And the base triads here are i, ii°, III+, iv, V, VI, vii°. And unlike diatonic minor which features a 7:7 note to triad ratio, in harmonic minor there are 2 major, 3 minor, 4 diminished, and 3 augmented. I'll leave this as an exercise to the reader to figure out...
- referring to 2nds 4ths and 6ths as extensions are not wrong. But in triadic context, I'm used to these extensions being referred as 9ths 11ths 13ths, with the former being more commonplace in the context of suspensions
- the minor 2nd/9th is a dissonant sound, along with other extensions you didn't mentions: #11 and b13. If you don't like the sound of a certain chord, experiment with different voicings.
- that would be a diminished 7th. also called a minor 7 flat 5.
GuitARBEn
Thank you for this comment!