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Descend as well.C system at the nut, where we've done some work. When we use this fingering, it substitutes well for the Dominant 7. In this instance, it will sound as a V9 without a root. Strumming chord scales is the 'academic' angle. At the start of mapping keys, keep triads and 7ths chord scales as separate exercises. Play them in order. For the jamming part, strum it all...triads & 7ths mixed. We can also endlessly tone toggle any of these chords. In fact, playing the 7ths, as in this lesson, is already a tone toggle, a swap, a change, a mod. For fixed position chord scales, we now have C and G mapped triadically and in 7ths, at the nut.
Bm7b5 is a rootless G9. G9 is adding an A tone to a G7 chord. The 12 bar blues can be played with just the m7b5 chord moving around.