I was recently told, that I should not consider ‘Bb, in the ‘C Ionian Scale, because: it does not exist in the, ‘C Major Scale…
http://www.fretjam.com/backdoor-progression.html
I think there are exceptions.
If the ‘Parent Major Scale of C is C, is the ‘Bb Major Scale’ compatible?
Hi Donn.
There will never be an exception. C major is C major, it doesn’t have a parent major scale because it already is the major scale. It can only have a relative scale, i.e., A natural minor, or it’s relative modes.
If you have a ii – V – I progression and substitute an alternate version of it, such as ii – bVII – I, then you are temporarily moving out of the key. The overall “feel” will still be C major, but for the duration of that “out of key chord,” you will be out of key as far as notes of the scale are concerned. At this point you could alter the C major scale or use some other idea but your usual “B” from C major will cause a lot of dissonance and probably sound like you have gone wrong.
You could try altering the C major scale by swapping the B for a Bb. This would essentially make it an F major scale but as we’re already (predominantly) in C major you could view this as C Mixolydian for the duration of the Bb major chord.
There’s probably a thousand ways you could think about it so it’s just about what works, and sounds well, for you. Personally I’m not really a jazzer so I would just play something Bb related over this chord, probably some form of Bb arpeggio. Either way, for the time spent on this chord, you are, strictly speaking, no longer in C major.
