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Major scales have a major third interval from the tonic of the scale to the 3rd scale degree.

I would expect the same to be true in minor with a minor third interval but, for example, in the pentatonic minor scale the minor third is from the tonic to the 2nd scale degree.

So, in the case of major scales:

How do you define what a minor scale is? And how do you know where the minor third interval is if it is always from the tonic to the same scale degree?

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  • Hmmm, a lot of well argued wrangling about the nature of scales, but in my (not particularly educated) mind the second note that appears in a pentatonic scale is the third tone of the ... "donor" (?) scale. Just as the second note that appears in a chord is the third of the donor scale, and that doesn't cause confusion. Pentatonic scales and chords are subsets of larger groups of notes, their constituents are described by referencing their place in the donor group. That's how my brain wraps around it anyway. :-) Commented Oct 20, 2023 at 11:54

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major scales have a major third interval from the tonic of the scale to the 3rd scale degree

Correct. That is why it's called a major scale.

I would expect the same to be true in minor with a minor third interval but, for example, in the pentatonic minor scale the minor third is from the tonic to the 2nd scale degree.

The numeric designation of interval size (third, fourth, fifth, etc.) is based on the diatonic scale. In the middle ages when these names arose, the pentatonic scale was not on the horizon as a theoretical construct.

That the second degree of the pentatonic minor scale is a minor third above the root makes sense if you think of the pentatonic scale as a diatonic scale from which two scale degrees have been removed. In the context of music theory derived from European tradition, at least, the pentatonic scale is a second-class citizen.

How do you define what a minor scale is?

In general, I suppose, a minor scale would be any scale that includes a minor third above the root (probably excluding those that also include a major third above the root), though I don't think this definition has been formalized, and since I am not familiar with the full catalogue of scale definitions used in jazz theory and derived theories, there could well be exceptions that I'm not aware of.

Certainly in the context of traditional classical theory, the three minor scales are simply the minor diatonic scale, the "natural minor" along with two scales that can be obtained through chromatic alteration of the sixth and seventh degrees, which are the harmonic minor and melodic minor. One also occasionally sees the Dorian and Phrygian modes described as "minor modes" because they have a minor third, so it would not be unreasonable to include them in a broad category of "minor scales," either.

And how do you know where the minor third interval is if it is always from the tonic to the same scale degree?

Remaining in the context of traditional theory, a minor third is simply an interval that spans three letters and comprises a distance of three semitones. If the root of your scale is C then the minor third is E♭.

(This gives another insight into the reason for not calling the second degree of the minor pentatonic scale some kind of "second" -- it would imply that for music using the pentatonic scale we would rename the notes using only five letters, redefining the frequency ratios between the letters. Of course, doing that would be massively confusing. So, for example, one minor pentatonic scale is A-C-D-E-G-A, where the second degree of that scale, C, is a minor third above the root, A.)

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  • Not sure about the description of a minor scale. C minor obviously does contain m3 - from ^1>^3. BUT - it does contain M3 - from ^3>^5. Maybe it's just the way the answer is phrased?
    – Tim
    Commented Oct 19, 2023 at 7:46
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    @Tim: Yeah I thought that - perhaps adding something along the lines of "as measured from the tonic" might make the intent clearer?
    – psmears
    Commented Oct 19, 2023 at 13:05
  • Thank you for your answer. But doesn't the natural minor scale, for example, include a major third, from the 3rd to 5th scale degree? So that definition wouldn't work in that case. Commented Oct 19, 2023 at 19:46
  • "it would not be unreasonable to include [Dorian and Phrygian] in a broad category of 'minor scales'" —In the context of the broader discussion that @MusicQuestions7 has been pursuing, I'm about ready to say forget this idea. You (musicQuestions7) are in search of an all-purpose definition of what makes "a minor scale," to which I think today I would say "Just plain old natural/harmonic/melodic minor, and that's it." This is about semantics, after all. In today's common practice, when we say "a minor scale," we mean one of those. In this sense "minor pentatonic" is not "a minor scale," it's Commented Oct 19, 2023 at 21:20
  • ... simply making use of the same word in its official identifier. I don't think we need an all-purpose textbook definition of what "makes a scale minor," because the word only means as much as common usage lets it mean. Commented Oct 19, 2023 at 21:20
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Pentatonic scales are a red herring.

The interval in a minor scale from tonic is m3,while that in a major scale is M3. That's about all there is to it. Pents do not feature in this equation.

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  • What do you mean with red herring? But how do you define minor scales that are not diatonic scales? Commented Oct 19, 2023 at 19:47
  • Minor scales are simply those which have m3 between tonic and ^3. So even C pent min is deemed a minor scale, because between C and E (b) C,D,E alphabetically, is m3. Similarly maj pents. and for that matter, modes will be known as major or minor. It's a Man-made decision, just like most theory.
    – Tim
    Commented Oct 20, 2023 at 7:36
  • Thank you, I understand now. Commented Oct 20, 2023 at 10:44
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Minor and major refer specifically to the intervals in the diatonic scale and its modes. This does not necessarily hold true in other scales.

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  • OK, got it, but how do you define minor scales that are not diatonic then? Commented Oct 19, 2023 at 19:48
  • @MusicQuestions7 how many non-diatonic minor scales are you aware of?
    – phoog
    Commented Oct 20, 2023 at 7:05
  • @phoog I'm aware of the pentatonic, hexatonic and octatonic minor scale, and I would assume that there is a nonatonic minor scale as well. Commented Oct 20, 2023 at 9:02
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In my opinion, minor scales are scales where the minor third is present (relative to the root).

Examples of minor scales:

Aeolian

Dorian

Phrygian

Harmonic minor

Melodic minor

Hungarian minor

etc. etc.

The pentatonic minor scale is a minor scale to me. Since it contains a minor third. I think the confusion comes from thinking the third must be the third note of the scale. It's not. A third is an interval. It's named a third since it's usually the third scale degree but it doesn't have to be. Compare to the fifth in a pentatonic scale - it's actually the fourth note in the scale. It's still called a fifth.

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