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Reading between the scales

While looking for accessible information about the harmonic minor scales I stumbled upon this theory: “The notes outside the major scale form a pentatonic scale”

Wow. They actually do. Now, after thinking about this on my bus ride home, I concluded: It’s not strange at all. Removing 7 notes from the 12-note octave leaves 5 notes which form a new scale on their own. So, it seems that the theory applies to all 7 diatonic scales, not just the major ones.

A major:
A B C♯ D E F♯ G♯ (A)

??? pentatonic scale
A♯ C D♯ F G (A♯)

I tried to figure out what the new pentatonic scale actually is, but I think that it’s rather a mode of a scale. Which led to another question: “Are there different modes of pentatonic scales?”

It seems that there are 5 pentatonic modes that can be created from A♯/B♭, C, D♯/E♭, F and G:

Ionian        C E♭ F G B♭
Dorian        E♭ F G B♭ C
Phrygian      F G B♭ C E♭
Mixolydian    G B♭ C E♭ F
Aeolian       B♭ C E♭ F G

So, in the example above the pentatonic scale corresponds to the Aeolian pentatonic mode.


       A major scale        C minor pentatonic (Aeolian)

In the beginning I claimed that any combination of 5 notes between the 7 notes of any diatonic scale form a new pentatonic scale. I wasn’t sure so I tested the theory with the F♯ minor scale.

F♯ minor:
F♯ G♯ A♯ B♯ C♯ D♯ E F♯

??? pentatonic scale
F G B C D (F)

As indicated by the “???” I don’t understand how to name the new scales.

Learned musicians probably scoff at the mere thought of anyone not understanding this but for me all this was at least a very interesting discovery. Instead of using Google I tried to use my brain. If only I had a clue about implementing the theory.

I know too little about music theory to properly read between the scales.