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12 Essential Tunes
At this point, the tune takes a slight twist; instead of the ii-V7 progression in the previous two bars resolving to I as expected, bar 5 features a Gmaj7 chord. This is not an unusual move, dominant seventh chords occasionaly resolve up a whole step.
This section also modulates in an unexpected and therefore exciting way-it ascends a minor third.
You could of course improvise with a G scale over the GMaj7 chord and with the Ab scale over the Bbm7-Eb7 change (another ii-V7).