Because all the harmonic structures of this piece are closely related, finding the guide tone lines for Alan Mencken’s Colors of the Wind is a simple matter. But before going further, it will be helpful to review what is meant by “closely related.”
Closely related harmonic structures (chords) are those that share many pitches in common. The most obvious example is a tonic and its relative minor – in this case, Db major and Bb minor. They share a common key signature (five flats), and the only difference between the basic triads is that the fifth of Db major is raised a whole step to become the tonic of Bb minor.
In fact, if you were a guitarist in an ensemble who is asked to play a Db 6 in a jazz or pop context, you could save yourself some trouble and simply play a Bb minor triad over the Db bass. By the same token, if you were asked to play a Bbm7, you could just play a Db triad over a Bb bass. The major 6th chord and its relative minor 7th chord are identical from a harmonic, if not functional, standpoint.
A slightly more distant – but still close – relative is the iii chord, which in the present example is F minor. Once again, we only need to move one pitch of the tonic to change the harmony. In this case, we lower the root pitch of Db one-half step to C, creating the F minor triad in second inversion.
Going from F minor to Bb minor requires that we raise the third a whole step and the fifth a half step, which become root and the third of the latter. From there, getting to Gb major (the IV of Db major) is done quite simply by raising the fifth a half-step.
Gb major to its own relative minor of Eb minor is also quite easy; raise the fifth a whole step to become the root of the new harmonic structure.
From Eb minor to Ab is another easy transition; simply raise the third and fifth a whole step (and if you want to make it an Ab 7 , you can leave the third alone and let the bass deal with the root).
Normally, Ab 7 would resolve to Db. In this case, Mencken writes what music theorists call a “deceptive” resolution, because the V7 here resolves to something other than I. It’s not too deceptive, however; Bb minor is still relative to Db major, so it’s not as jarring as it would be if it had gone to a distant common-tone chord such as E major (something that classical composers do regularly).
Menken uses the same harmonic structures in the B section, simply in a different order. Based on the information presented here today, can you discover the guide tone lines for that section of the song?
In the next post, we’ll look at the bridge.