Three's a Pair! - Part 2
Melodic Minor Triad Pairs - "Rhythm Changes" Bridge
As mentioned in that article, the pair of adjacent triads which most captures the sound of Melodic Minor are the Major & augmented triads, built off of the 4th and 5th scale steps, respectively.
(In C Melodic Minor = F Maj.(F-A-C) & G aug. (G-B-Eb) triad pair).
However, the quality of the pure diatonic triad built on 5th step of Melodic Minor is not augmented, but Major - G Maj. = G-B-D, which is exactly the same in C Major.
In fact, he only augmented triad occuring diatonically in Melodic Minor is based on the 3rd scale degree, or Eb (Eb aug. = Eb-G-B) in C MM.
Because the inversions of an augmented triad are symmetrical, G aug., Eb aug. (as well as B aug) are all interchangeable. I just thought it more accurate, given the diatonic nature of the augmented triad in MM, to refer to it as forming from the 3rd scale degree, rather than the fifth.
Regardless how you call it, the premise of this exercise is based on the bridge - the middle 8 bars - of "I Got Rhythm" changes.
Because the harmonic structure of these eight bars is made up of 4 dominant 7th chords moving along the Cycle of Fifths at a rate of 2 bars apiece, the exercise can be pieced together in groups of 3 to complete a full cycle.
Anyway. it breaks down like this:
Line 1, Measures #1 & 2- The first line is simply made up of ascending triads, with one inversion. Since the bridge to "Rhythm Changes" begins on the III7 of the key in question, we're looking at E7alt in this case (Rhythm Changes in C).
Since the "altered scale" of choice for this E7alt would be - you guessed it - the E altered scale, or the 7th mode of F Melodic Minor, the triad pair derived from the 3rd & 4th degrees of F MM are Ab aug. & Bb Maj. In this case, however, we begin the line on the Major triad, which doesn't really impact its overal tonal flavor.
Measure #2 continues the ascending line, offering the next inversion of both the Bb Maj and the Ab aug. triads.
Line 1, Measures #3 & 4 is similar to the first 2 bars, with chord, scale, and triad pair transposing down a Perfect 5th (or up a P4th) - A7alt = Bb MM = Eb Maj. & Db aug. triad pair.
Line 2, Measures #5 & 6 is a bit different in that the line begins with a descending augmented triad. The triads change direction and rhythmical shifting is employed as it spirals downwards.
As in the previous measures, each chord, scale and triad pair transpose down P5th from the last.
Measures #5 & 6 - D7alt = Eb MM = Ab Maj. & Gb aug. triad pair.
Measures #7 & 8 - G7alt = Ab MM = Db Maj. & B aug. triad pair.
I guess the "Rhythm Changes" part of this exercise is really only incidental. The real purpose is to practice Melodic Minor triad pairs over dominant 7th chords through the Cycle, and this works well on the bridge of "Rhythm".
Try alternating the order and direction of the Maj. and augmented triads, as wel as of the line itself.