Unlock the Harmonic and Melodic Minor Scales with the Rectangle and Stack

This lesson has been requested a few times by my newsletter subscribers. If you've already got your head wrapped around the rectangle and stack approach to the pentatonic scale, it's straightforward to use that knowledge to play the harmonic and melodic minor scales across the entire fretboard. Check it out and ask your questions in the comments!

Unlock the harmonic and melodic minor scales

with the rectangle and stack

The harmonic minor scale is often used when a dominant V chord resolves to a minor chord. It’s common in jazz (e.g., when soloing over a minor ii-V7-i), and it also shows up a lot in metal and neoclassical metal music.

The V-i sequence simply can’t happen inside one of the major scale modes. In the Aeolian (natural minor) and Dorian modes, the fifth diatonic chords are minor triads (or m7), and in the Phrygian mode, the fifth diatonic chord is a diminished triad (or m7♭5). So, we need a different scale to use in these situations.

The scale that fits the bill is the harmonic minor. It is often described as a natural minor scale with a raised (natural) seventh. Here are the two scales side by side, each on one string:

The related melodic minor scale is usually described as a natural minor scale with both the 6th and 7th raised a half-step or as a major scale with a flattened third. I prefer to think of it as the Dorian mode with a raised (natural) seventh, and you’ll see why in a moment. Here they are side by side:

The rectangle and stack revisited

One of the big advantages of the rectangle and stack approach to the pentatonic scale is that it is easy to add two notes to turn a pentatonic scale into a major scale mode. If this gets confusing, you may want to revisit the rectangle and stack and the ”hidden in plain sight” videos to refresh your memory.

Inside the rectangle, we can add two notes in a staggered pattern to create the Aeolian mode:

With both notes shifted toward the bridge, we get the Dorian mode:

Similarly, inside the stack, the two notes are staggered to create the Aeolian mode and shifted up and toward the nut to create the Dorian mode.

The modified rectangle and stack

To use this approach to play the harmonic and melodic minor scales, we must raise the flat seven by a half step. This stretches out both the rectangle and stack and changes the minor pentatonic scale into what you could call the “minor major pentatonic scale,” although there isn’t a generally accepted name for it.

The added notes fall in the same places as they did with the original rectangle and stack.

An alternative approach

In some situations, moving the natural seventh up a string may make it easier to play what is increasingly difficult to justify calling a “rectangle.”

Here, the added notes stay in the same place relative to the root and fifth.

Vertical connections

To play these scales across the fretboard, we must connect them vertically. Recall that rectangles and stacks alternate vertically. Here is how they would lay out on a 10-string all-fourths fretboard (roots for the minor pentatonic scale are shown in red):

Note that the stack is "nut"-aligned with the rectangle below it and "bridge"-aligned with the rectangle above it. This is always the case, although sometimes the upper shape is shifted over one fret by the warp. Also take note of the relationships between the root locations. Roots are always a +2, +2 or a -3, +3 move on the all-fourths fretboard.

Although it may look more confusing, the same relationships hold true for the modified “minor major” rectangle and stack:

The alternative “rectangle” makes the alignment a bit harder to visualize, but the roots stay in the same places.

Once you have the modified rectangle and stack under your fingers and understand how they connect vertically, you can play the harmonic and melodic minor scales in five positions on the fretboard.

You can use either of the modified rectangles to re-create in-position fingering patterns. I find the ones based on the alternative rectangle to be a little easier to play, but you should try both and decide for yourself. Here are the alternative rectangle fingerings for the harmonic minor scale:

And here are the corresponding fingerings for the melodic minor scale:

I recommend trying both versions of the “rectangle” and stick with the one that works best for your fingers.

Diagonal movement

With a small extension, the “minor major” rectangle works well for diagonal movement on the fretboard, yielding two useful pathways for playing three-octave versions of these scales. As a reminder, on an all-4ths fretboard, any shape can be moved up two strings and over two frets and repeated an octave higher. For the pentatonic rectangle, it looks like this:

For the “major minor” rectangle, we get:

And for the alternative “rectangle”:

As we did before, we can fill in the two extra notes to create a harmonic or melodic minor scale. However, since the rectangle doesn’t include the fourth note of the scale, we’ll have to add that as well, so we get a 3+4 note repeating pattern. And, of course, we must always remember to take the warp into account.

The most finger-friendly way to play three-octave versions of these scales is probably to use the alternative “rectangle” and add the fourth on the lower string:

You can take a similar approach with diagonally connected stacks, but those patterns are less finger-friendly.

Summary and how to practice

If your name is not Yngwie Malmsteen, it is probably not necessary to be able to play three-octave harmonic and melodic minor scales on demand. Instead, I recommend learning how to build the harmonic and melodic minor scales around the modified stack. Then, choose either the trapezoidal or triangular version of the “rectangle” and learn that thoroughly as well.

Once you have both of those under your fingers, practice how they connect vertically. Once that is under your fingers, you can call up a harmonic or melodic minor scale anywhere on the fretboard by finding a root, laying down the appropriate rectangle or stack, and going from there.

Happy shredding!