Very cool Joe!
If I might elaborate a little for others who find these voicings a
tad complex...there is actually a mini lesson in this:
Here are versions of those voicings WITH the root added as the
In A7alt, the F melody note functions as the #5, and in the Eb9 it
functions as the natural 9th.
In Ab13, the F melody note functions as the natural 13th (notice
there is also a 9th present in the voicing, no 3rd), and in the
D7alt, F functions as the #9.
These chords are known as "b5 substitutes". The rule is this: for
any functioning dom7 chord, you may substitute another dom7
chord whose root lies a b5 away.
This is a great way to get maximum mileage out of your dom7
chords since they essentially share the same notes. The reason
this substitution works is because both chords share a common
interval know as the tritone:
This is a very important interval to get to know. When you
analyze it you will find that the tritone becomes inverted in the
b5 substitute dom7...for example, in the A7 the G note is the b7
and the C# is the 3rd, but in the Eb7 the G becomes the 3rd and
the C# (now spelled enharmonically as Db) becomes the b7.
Another note of interest is how the upper tensions react...in one
voicing the 5ths and 9ths are natural while in the other they
b5 subs really become useful for generating smooth voice
leading in chord changes.
If this is too complicated for some of you, no worries....it's just
food for thought. In any event...blame Joe!
Thanks for the great voicings Joe,