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Recalling the scale of F major, we know that the chord
on I is FΔ7, F:A:C:E. If we rearrange the notes of this
chord so that they begin with A, we get A:C:E:F. This
is the first inversion of the FΔ7 chord.
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Notice
how close this voicing of FΔ7 is to the chord on III,
A-7, which is A:C:E:G. In fact, in very many harmonic
situations, FΔ7 and A-7 are practically interchangeable.
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Similarly the first inversion of II, G-7, is close to
the chord on IV, BbΔ7. C7 and E are also related, as
are D-7 and FΔ7. Note that the first inversion of D-7,
F:A:C:D, is sometimes given the symbol F6 (work it
out!).
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So we
have three little families of chords within the
harmonised major scale. FΔ7, A-7 and D-7 (that is, I,
III and VI) form one grouping. G-7 and BbΔ7 form
another (II and IV). And the third is C7 and EŘ (V and
VII).
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Now we
can understand the origin of one common variation of the
II-V-I theme (as seen in, for example, Little Suede
Shoes). Instead of
| G-7 | C7 | FΔ7
|... we have | G-7 | C7 | A-7 |
in which the FΔ7 is
substituted by another member of the same family, A-7.
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This in
turn allows us to extend the pattern and close the cycle
of fifths:
| G-7 | C7 | A-7 |
D-7 | G-7 | C7 | A-7 | D-7 |... and so on. The A-7
chord thus does two jobs. It behaves like an F chord
onto which the C7 resolves. At the same time it starts
a nice cycle of fifths (an A chord followed by a D,
followed by a G, followed by a C, followed by an
F/A...and so on, for ever if needs be).
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One
more adjustment to the basic pattern will complete the
story of II-V-I (at least for now!). Notice that the
minor 7 chord on G is followed by the dominant 7 on C.
What would happen if A-7 were to be followed not by the
minor 7 on D but, in an echo of the G/C pattern, the
dominant 7 on D?
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The
answer is - one of the the most common variations on the
cycle of fifths pattern encountered in jazz:
| G-7 | C7 | A-7 | D7
|
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Of
course, this progression throws a spanner in the works
because D7 is no longer a chord of the harmonised F
major scale. It has an F# where D-7 has an F.
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Something to experiment with - how do you improvise
against D7 in this progression. What would be its
improvising scale...? |