Melodic Minor with a b5 or b4?

In my last post the Melodic Minor b5 scale cropped up unexpectedly; I wasn't expecting this so I dug into it a little bit. On paper I found quite a few interesting properties, but when I sat down with the guitar it became obvious that this was something very familiar. And then a little more experimentation revealed something more interesting.

Melodic Minor b5 is what it sounds like: 1 2 b3 4 b5 6 7. I'll skip all the working-out I did of modes and covers and suchlike. What you need to know is what I discovered when I "felt" how the scale laid out on the fretboard:

     Whole-Half:       1 2 b3 4 b5 #5 6 7
     Melodic Minor b5: 1 2 b3 4 b5    6 7

It's an octatonic diminished scale with one note missed out. Any time Melodic Minor b5 pops up, this is probably the way I'll think of it, since I'm already very familiar with that scale and skipping a note really doesn't add much variety.

[EDIT: A few months after writing off Melodic Minor b5 in this way I discovered that one of its modes, a Lydian with b3 and #5, is the basis of Jimmy Wyble's Etudes 17 and 20. So there you go: never write anything off!]

This made me take a quick look at the other "altered-note" versions of Melodic Minor -- the ones you get from changing just one note of the scale and leaving everything else alone. And I'm particularly interested in the ones you can't get by doing the same thing with Major or Harmonic Minor.

There are only three possibilities. One is Melodic Minor b5. Another is Neapolitan, which is an old friend to me. The last is Melodic Minor b4, and this is a beautiful scale, very pretty and with a strongly "Major scale" sound despite being two alterations away from it. This, not Melodic Minor b5, is the interesting member of the family, and for some reason I'd always neglected it.

Melodic Minor b4 itself is of course most easily heard as a major scale, with the b4 functioning as 3, but you can definitely phrase it as a minor scale with a genuine b4 as well if you wish. This, Mararanjani (1 2 3 4 5 b6 bb7) and Dorian b5 bb6 (1 2 b3 4 b5 bb6 b7) offer pretty and very accessible melodic lines.

Likewise, Superaugmented ##4 (1 #2 #3 ##4 #5 #6 7) won't scare the horses; it looks fearsome but it's really just a fancied-up minor pentatonic:

     Superaugmented ##4:    1 #2 #3 ##4 #5 #6 7
     Respelled:             1 b3 4   5  b6 b7 7
     Minor Pentatonic:      1 b3 4   5     b7

Adding the 7 as a passing tone to Minor Pentatonic is common enough; the b6 is one step away from natural minor, so although it lives in a slightly different stylistic space it's hardly a rarity.

Further out are Gamanashrama Augmented (1 b2 3 #4 #5 6 7) and Super Locrian bb5 (1 b2 b3 b4 bb5 b6 b7). The former is Lydian Augmented with a b9, surrounding the root with semitones like Neapolitan does; an acquired taste but a strong and distinctive one. The latter looks like an "altered dominant" thingy, but the bb5 (=4) gives it a very wonky quality indeed.

Finally, and in some ways furthest from familiar territory, is Vanaspati (1 b2 bb3 4 5 6 b7). There's no major or minor triad to provide a simple harmonic context, and it has a sequence of semitones ascending from the root that denies us anything much in the way of a leading-tone function.

CAGED diagrams for all these are of course in the book but I think the easiest way to learn these is via the Minor Pentatonic with two added notes. Here's the full-fingerboard diagram with Minor Pentatonic in blue and the two added notes in yellow and green. They're pretty easy to find: