> How do you understand the 2nd 4 bars of the bridge?
> |Ab7 |Ab7 |Dm7 |G7 |
Pedro said the essential thing. It's "dominant preparation" for the returning
key of C. The essential chord progression there is Ab7 - G7; the Dm7 is
interpolated either to "prolong" the G7 or provide a strong root movement: Ab
- D - G.
Ab7 - G7 is known in legit circles as "augmented 6th chord going to dominant
7th." Reason for Ab7 being called "augmented 6th" is another story: an Ab7
resolving down a half step to G invites Ab7's Gb to be spelled as F# because
the F# may lead melodically up to G. Of course the interval from the Ab root
up to F# is an augmented 6th.
There are a couple of other fairly common situations (both jazz and legit) in
which an Ab7 might actually be written with an F# rather than a Gb: Ab7 - Eb
or Ebm and Ab7 - C or Cm.
in any case, we all should get used to Mm7 chords (dominant 7th structures)
moving by various intervals, with or without "II7" chords interpolated before
any Mm7.
Roger McDuffie