What are a few things that can be done when an altered dominant chord presents itself in a tune? The first notion to be aware of is that the altered chord derives from the altered mode, otherwise known as mode VII of melodic minor. Below are a few tricks to break out of the diatonic sound of the scale (i.e. by introducing intervallic leaps in addition to the stepwise motion inherent to seven-note scales), and gain a little freedom with it. We will use Eb7alt as an example throughout this post.
First, let’s have a look at 5 different triads that can be played in the context of upper structure triad voicings (USTs) for an altered chord. We’ll use these triads as “numerators” of the UST voicings, the “denominator” always being the basic chord sound (i.e. chord tones 1, 3, and b7 sounded together):
- I°
- bIImi
- bIIImi
- bV
- bVI
Both minor triads on the one hand, or both major triads on the other hand, can be combined to form two distinct hexatonic scales, which can in turn be used as interesting melodic devices to play lines over the altered chord:
- Hexatonic 1 = bIImi + bIIImi
- Hexatonic 2 = bV + bVI
Granted, these two hexatonics are only slightly different. Let’s put them under the microscope:
| Hex. 1 | Emi + F#mi | E F# G A B C# |
| Hex. 2 | A + B | A B C# D# E F# |
The only difference between the two scales is that hexatonic 1 has a G (and no D#), while, conversely, hexatonic 2 has a D# (and no G). From an additive point of view (when both hexatonics are combined), we fall back onto the full, seven-note altered mode (D# E F# G A B C# D#) derived from melodic minor (E F# G A B C# D# E). But looking at the two hexatonics from a subtractive viewpoint (taking the G and the D# out of the scales), then the fact that we are left with the same five notes (E F# A B C#) becomes apparent. These notes make up a pentatonic scale (bIII minor pentatonic/bV major pentatonic relative to the degrees of the altered mode), which can also be used as an even more angular melodic device, in the sense that it is more salient than the hexatonics from an intervallic perspective:
