Hi, so I have been combining the IFR numbers method with the theorical jazz way of changing scales for every single chord and it’s been fun, but I’ve sort of reached a roadblock where it feels like I cannot really mix both of them; This topic is called substitute dominants.
So, lets say we’re playing in C major (meaning that C is the 1, D the 2 and so on) and we have a very common progression like Db7, Dm7 and Cmaj7, which would be translated as bII7, iim7 and Imaj7 in the IFR numbers method.
Now, I’ve been taught to use a mixolidian #11 scale when improvising over a sub-dominant chord, which would in turn en up on the following scale:
Db7 Mixolidian #11: Db - Eb- F - G - Ab - Bb - Cb
In IFR Numbers: b2 - b3 - 4 - 5 - b6 - b7 - b1
It just seems so outside the key that it actually feels counter productive to keep thinking of the C as the tonic center, but the whole point of mixing the IFR with the traditional Jazz way of playing is to avoiding leaving the main scale unless strictly necessary (modulations). I’ve been able to play secondary dominants with this approach because you just have to change the b3 of the chord into a major 3rd; meaning that for VI7 you just have to change one note of the scale; in this case you would change the 1 to a #1 (because 1 is the b3 of 6) and that would leave us with a A7 Mixolidian b6 without even having to stop thinking about the C major scale.
So I don’t really know how to keep this way of playing with the sub-dominants. Should I just play the scale of the chord they’re doing the substitution for? Meaning that in the case of Db7 I could just play G mixolidian. Or should I just memorize the 5 scales that happen with these chords? Meaning that I would need to memorize the changes that the bII7, bIII7, bV7, bVI7 and bVII7 create over the tonal center? I’ve also thought of only changing the tonic, 5th and 7th of the chord (making Db7: b2 - 3 - 4 - 5 - b6 - 7 -b1) but that would create a mixolidian #9, #11, #13 and I don’t really know if that sounds good (I’ll have to test it out).
I don’t really know what I should do, but these kind of theorical problems are fun.
I would really appreciate your imput