Long time without writing anything here. New category, music composition/improvisation tips, since I’m forgetting continuosly this kind of tricks that I’m using on impros.
So, a sort of dominant substitution trick that i’ve extracted from Vincent Randy’s Introduction to jazz (A quite complex book to be considered an Introduction, tbh)
So first trick that I don’t want to forget: On guitar, a (I) 7b9 chord can be converted to a (V) °7 chord just by using the second inversion.
Since both chords have a Dominant function, but towards different grades, this can be used to modulate easily.
Example:
Given a C7b9, this is a dominant chord that would solve to F(major/minor/min7, whatever).
C7b9 usually is fingered on guitar droping its fifth, just playing C E Bb and Bb.
We can add that dropped fifth using the bass strings for it (usually, that would be on the lower string that is playing the root. If C is on the 3rd fret on the 5th string, G is on the 3rd fret of the 6th string)
If we do that we’re dropping the root. The chord is now rootless.
If we take a look to the notes that we’re playing now, they’re:
G E Bb and Db (since we dropped the C)
And what are the notes of G°7?
Just the same!
G Bb Db and E
So now, we can use the initial C7b9 to move towards F, but we could also use C7b9/G to move to Abminor (interpreting G°7 as a VII degree on an harmonic minor scale )