Altered Scale

In my last article, we briefly discussed the altered scale as a mode to the melodic minor scale. However, there's much more to discuss around this scale – how it's constructed, its relation to even more scales, and, most importantly, examples of it in action – so that's exactly what we'll do in today's article. Let's get started!

Constructing the Altered Scale

To review, the altered scale is constructed below. As usual, we'll do this in C major for the sake of example:

At first glance, this scale looks strange, as it doesn't look similar to either the major or minor scale. One not-so-obvious way to create this scale is to take the major scale and lower every scale degree by a half-step apart from the tonic, but this doesn't tell us anything meaningful. However, note the last line of "Extended Scale Degrees," which contains scale degrees that go past the octave – this will give us some insight in how this scale is applied in context. For now, let's find some other scales that we can compare with the altered scale in order to ground this discussion.

Altered Scale vs. Melodic Minor Scale

We've alluded to our first scale at the start of this discussion – recall that the altered scale is a mode of the melodic minor scale. Let's take a look at the two scales below:

We can clearly see that if we take the D♭ melodic minor scale, and begin on C instead, we end up with the C altered scale – that is, the altered scale is a mode based on the seventh degree of the melodic minor scale (much like how the Locrian scale is the same for the major scale).

Altered Scale vs. Locrian Scale

Speaking of the Locrian scale, this is our next scale to compare. Once again, we'll compare the two scales below:

Once again, these two scales are nearly identical, with the exception of the diminished 4th in the altered scale (F♭). In effect, the altered scale took the Locrian scale, an already dark-sounding scale with nearly all minor or diminished intervals (except for a perfect 4th in C-F), and made it sound even darker (by diminishing the 4th). This is why the altered scale is sometimes referred to as the "Super Locrian" scale.

Altered Scale vs. Mixolydian Scale

The last scale we'll compare is the Mixolydian scale. Like before, both scales are below:

The relation between these two scales isn't quite as obvious as the last two – to explain this one, let's refer back to the "extended scale degrees" from earlier:

Traditionally, the root, major 3rd, and minor 7th are the intervals that give the dominant chord its signature sound – furthermore, in jazz, dominant chords are often played with their natural extensions (the 9th, 11th, or 13th). From the root of any dominant chord, the altered scale contains the three signature intervals, and the "altered" extensions (that is, raised or lowered by a half-step).

To explain in detail – we can see the root and minor 7th clearly in the above diagram. The diminished 4th interval is enharmonically equivalent to a major 3rd, giving us our dominant chord. Finally, our altered extensions come from the flat 9th, sharp 9th, sharp 11th (or flat 5th), and flat 13th (or sharp 5th) intervals. It's for this reason that the altered scale can be referred to as the "altered dominant" scale. This is also why soloists in jazz can use the altered scale as a method of playing "out" when soloing over dominant chords, and also explains the usage of altered chords as a more tense substitute for dominant chords in songwriting.

Altered Chords in Action

There are several examples in jazz of soloists using the altered scale when improvising, but there are some particularly rare and interesting examples of this idea in popular music. Our first example is Stevie Wonder's "Isn't She Lovely" – in particular note the second chord in the bridge, around the 0:26 mark ("I never thought through love, we'd be…") – it's a G♯^7♭9♭13 chord, which acts as a dominant chord to the following C♯m⁷ chord. You can hear the flat 9th (A) in Wonder's vocals, and you can hear the flat 13th (E) in the electric piano. Check it out below:

Our second example is actually a subversion of everything we've discussed so far, and it comes from none other than legendary guitarist Jimi Hendrix. While "Purple Haze" is the song we'll be discussing, note that "Foxy Lady" or other similar tunes would fit here as well.

We'll be talking about the famous "Hendrix chord," which you can hear in "Purple Haze" around the 0:24 second mark. Believe it or not, this is actually an altered chord – specifically, an E^7♯9 chord! Note however, that this chord is not used as a dominant chord – in fact, it's the tonic chord, as the tune is in the key of E. While this disregards much of the theory we discussed earlier, it does line up with the blues tradition – using dominant 7th chords as the tonic is common, and the sharp 9th (in this case, G in the key of E) works well to highlight both major and minor tonalities, in a similar fashion to the blues scale. This ultimately gives the chord a dirty, but not entirely dissonant, quality. It truly goes to show that, in true rock 'n' roll fashion, some rules are meant to be broken.

Conclusion

Altered scales and chords are a great way to add flavor to dominant chords, and are a valuable tool in adding stronger tension and release in songwriting. We've discussed how to construct the scale, comparisons to scales we've previously discussed, and shown some examples of them in action. Try them out in your next composition and see where they take you!