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  • The Ionian mode which is the Major scale - is the second mode of the minor pentatonic scale (the Major pentatonic scale) plus a Perfect 4th and a Major 7th notes. It is also a combination of, for instance, the 5th mode of the minor pentatonic scale and the 4th pentatonic mode a half-step down.

  • The Dorian mode is the minor pentatonic scale plus a Major 2nd and a Major 6th. It is also a combination of the 1st and 5th modes of the minor pentatonic scale.

  • The Phrygian mode is the minor pentatonic scale plus a minor 9th and a minor 6th. It is also a combination of the minor pentatonic scale and the major pentatonic scale a half step up.

  • The Lydian mode is the Major pentatonic scale plus a sharp 4th and a Major 7th, and it is a combination of the major pentatonic scale and the minor pentatonic scale a half-step down.

  • The Mixolydian mode is the Major pentatonic scale plus a Perfect 4th and a minor 7th and is a combination of the Major pentatonic scale and the 3rd mode of the minor pentatonic scale.

  • The Aeolian mode is the minor pentatonic scale plus a Major 2nd and a minor 6th. It can be seen as, among other things, a combination of the 3rd and 4th modes of the minor pentatonic scale.

  • The Locrian mode is the 4th mode of the minor pentatonic scale plus a minor 2nd and a flat 5th. It is also the combination of the 4th mode of the minor pentatonic scale plus the 5th mode a half step up.

where the first minor pentatonic mode is 1 b3 4 5 b7

How would yall go about connecting the dots in terms of forming modal sounds and chords mixing pentatonic modes like this ?

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  • 1
    I'm not clear on what you're trying to do. Modulate between two pentatonic scales? Compose using diatonic modes? Why is it important to your question that diatonic modes can be broken down into combinations of pentatonics?
    – Aaron
    Commented Dec 10, 2023 at 6:04
  • 1
    @Aaron heyy, so i was mixing major and minor pentatonics on guitar for the blues licks and all, then i found out about this nugget a couple of mins ago and I m trying to connect dots and see the colors of the modes thru pentatonics
    – Mike Hawke
    Commented Dec 10, 2023 at 6:31
  • Are you using the same root note for each mode, or the same diatonic notes from one parent key?
    – Tim
    Commented Dec 10, 2023 at 10:11
  • @Tim I don't think that affects the answer. Any diatonic collection breaks down into the same two pentatonic scales, adjusted for rotation.
    – Aaron
    Commented Dec 10, 2023 at 10:22
  • @Aaron - OP mentions Aeolian and Locrian. Notes from A Aeolian are not the same as those from A Locrian, I think.
    – Tim
    Commented Dec 10, 2023 at 11:11

2 Answers 2

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TL;DR

There are four combinations of major and minor pentatonics which create the entire diatonic collection.

  • Two minor pentatonics a whole step apart
  • Two major pentatonics a whole step apart
  • One minor and one major pentatonic a half step apart
  • One minor and one major pentatonic a perfect fourth apart

However, any one of these formulations will suffice, as they all have identical pitch content.


Deconstructing diatonic modes into pentatonics

Let's restart from the inverse question: how can diatonic modes be deconstructed into two pentatonic scales?

Since all diatonic modes are rotations of each other, it's sufficient to consider a single mode, so let's use ionian (major).

Here is a map of the ionian mode on C along with the diatonic scales that can be derived from it. The numbers indicate the starting points of the nth mode, where ionian and major pentatonic are, respectively, mode 1.

  1 2 3 4 5 6 7 1 2 3 4 5 6 7 1
  C D E F G A B C D E F G A B C
1 * * *   * *   * * *   * *   *
2   *   * * *   * *   * * *   *
3     *   * * *   * *   * * *  
4       * * *   * *   * * *   *
5         * * *   * *   * * *
6           *   * * *   * *   *

What this table shows is ionian can be composed from:

  • min pent on ionian deg 2 + min pent on ionian deg 3 (2-4-5-6-1 + 3-5-6-7-2)
  • min pent on ionian deg 2 + maj pent on ionian deg 5 (2-4-5-6-1 + 5-6-7-2-3)
  • min pent on ionian deg 3 + maj pent on ionian deg 4 (3-5-6-7-2 + 4-5-6-1-2)
  • maj pent on ionian deg 5 + maj pent on ionian deg 4 (5-6-7-2-3 + 4-5-6-1-2)

But consider that the pentatonics built on ionian degrees 1/6, 2/4, and 3/5 contain identical pitch content, respectively. Further the pitches missing from 1/6 form a tritone, which is not contained in any maj/min pentatonic scale. This means there is really only one way to build the entire ionian (and by extension, diatonic) collection:

  • minor pentatonic on X + minor pentatonic on (X + M2)

Constructing diatonic modes from pentatonics

Now let's consider the minor pentatonic scale and look at how to construct the diatonic collection. The X axis is the diatonic collection, the Y axis is modes of the minor pentatonic. (Note that this is equivalent to considering the major pentatonic, with appropriate rotation.)

                       V____________________V
  1  2  b3 4  5  b6 b7 1  2  b3 4  5  b6 b7 1
  A  B  C  D  E  F  G  A  B  C  D  E  F  G  A
1 *     *  *  *     *  *     *  *  *     *  *
2                *  *  *     *  *     *  *  * 
3 *  *     *  *     *  *  *     *  *     *  *
4             *     *  *     *  *  *     *  *
5       *  *     *  *  *     *  *     *  *  *

As can be seen, the only minor pentatonic mode that can be mapped to diatonic degree 2 is mode 3, and only modes 2 and 5 can be mapped to diatonic degree b6. But the pitch content of modes 2 and 5 is identical; thus, we have

  • diatonic collection = minor pentatonic mode 2 + minor pentatonic mode 3,

which is identical to the formulation in the previous section.


Incorrect formulation

The Aeolian formulation is correct, but Locrian can not be decomposed into a minor pentatonic and a minor pentatonic a half-step up, regardless of the modes used.

Minor pentatonic = 1 b3 4 5 b7
Minor pentatonic + m2 = b2 3 b5 b6 7

Sum = 1 b2 b3 3 4 b5 5 b6 b7 7 (Too many pitches)
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  • Can you give a concrete musical example where this has been applied? Like something that could actually be played on an instrument. :) Is it like, if I play the notes of D minor pentatonic and E minor pentatonic, then I have played all 7 notes at least once, and thus explicated all notes of C major and its modes? The same with chords Dm7add11 and Em7add11. Or scales E minor pentatonic and F major pentatonic. And the musical application would be, how to use pairs of pentatonic scale shapes to explicate diatonic modes. Commented Dec 10, 2023 at 12:11
  • "Locrian can not be decomposed into a minor pentatonic and a minor pentatonic a half-step up, regardless of the modes used" - if you're allowed to use modes of pentatonic scales, and if that means shifted rotations, then it can be done. 4th mode of E min pent B-D-E-G-A, and 5th mode of D min pent, C-D-F-G-A, you get all 7 notes of B Locrian. In theory. But in practice, I suspect it will take a lot of skill and a strong B bass pedal tone to make it sound like B Locrian. Commented Dec 10, 2023 at 12:47
  • 1
    @piiperiReinstateMonica I’m not aware of any practical use of this, nor is it clear to me how OP intends to use it. Also D and E are not a half-step apart. I interpret OP as meaning that the roots of the two scales are a half step apart, though I see how you got your interpretation. It seems clarification is needed on both points.
    – Aaron
    Commented Dec 10, 2023 at 15:36
  • Yes, B and C, which would be the roots of those "pentatonic modes", are a half-step apart. I actually tried out this system, and it's a bit strange, because in order to make the proper modal sound you want to be able to use the characteristic tones, but maybe they're not available at the same time in either one of the pair of pentatonic scales chosen. Like in my example, if you want to use B, you can't use C and F at the same time. So you'll have to switch between the two scales relatively fast. It's certainly a way to make some kinds of colors. Commented Dec 10, 2023 at 15:50
  • 1
    @piiperiReinstateMonica I understand your construction but wasn’t clear myself. By “root”, I meant “of the major or minor pentatonic from which the mode is taken.” So I would have said you’re using D and E minor pentatonics, which, obviously are not a half step apart. I’ve asked OP for clarification.
    – Aaron
    Commented Dec 10, 2023 at 15:56
0

I don't really do this kind of music, but I've been watching videos about techniques like triad pairs and constructing scale patterns with seemingly arbitrary rules, so the system described here seemed somewhat interesting. Triad pairs... scale pairs?

I tried to produce a modal sound using a system where a pair of pentatonic scales is selected so that when their notes are combined, all seven notes of a diatonic scale are covered. As a target mode, I selected B Locrian, and as the two pentatonic scales, (1) the 4th mode of E minor pentatonic, i.e. root on B, and (2) the 5th mode of D minor pentatonic, root on C. Then I tried to construct licks with these two scales.

Here's a one-octave box of scale 1:

scale 1 box

And scale 2, close to the same position:

scale 2 box

First, a lick using the B-rooted scale, the 4th mode of E minor pentatonic scale.

Lick 1, B something pentatonic scale

Then a lick using the C something scale, which is also the 4th mode of F major pentatonic, and the 5th mode of D minor pentatonic scale.

Lick 2, C something pentatonic scale

(In Guitar Pro, the C something scale seems to be called "C Mixolydian Pentatonic". But in what sense is that C Mixolydian anything, if there's no Bb or E in it? It makes no sense to me.)

But does this combination work? In my opinion, in order to sound like B Locrian, at least B, C, D and F should be felt to exist in the harmonic context, maybe A as well. With our first pentatonic scale, we can reach B, D and A, but no C or F. But with the second scale, we get C, D, F and A. So if we could rely on someone else playing a low B, or if B has been imprinted in the listener's harmonic context as a root note very deeply some other way, we could be quite Locrian by simply using the C something pentatonic scale.

When writing the licks, I tried to emphasize the relevant notes of the selected "pentatonic modes", so that e.g. the C something lick wouldn't sound like it's in E minor, when played alone. The C something scale doesn't have a third in it, so it's hard to hear it as a mode as in "Church modes".

Anyway, if we play the two licks together and end the whole thing on a B note, the final note sounds like a home-note resolution.

Both licks together, ending on B

All in all, I think it's a plausible way of constructing lines, looking at a pair of pentatonic scales like a pair of chords that, when put together, form a modal scale.

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