I watched a video by the great fusion guitar player Tom Quayle* where he goes through using the Em pentatonic over D Dorian. Basically he is just playing level 3 notes over a level 2 harmonic environment and not playing the notes outside the pentatonic scale (1 and 4), but he makes it sound much more complicated than that.
This led me to think about minor pentatonic scales in terms of IFR:
Level 6 = 6 1 2 3 5
level 2 = 2 4 5 6 1
Level 3 = 3 5 6 7 2
A basic minor blues progression is 6 2 3 (i iv v ) so it’s really easy to improvise with lots of voice leading and chord tone targeting over it using IFR in this way. A Melody Paths Chart really helps to do this at first.
Even the common 3D variation of the minor blues progression becomes a piece of cake in IFR just by augmenting 5 to #5.
The minor pentatonic has a special sound so it is worthwhile (for me at least) not losing sight of it while improvising, although clearly improvising with all the notes of each level is good too.
Next, I must look at the major pentatonic and mixing the two over a major blues progression, but I have quite a few weeks of minor blues investigation still to do .