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I saw in this Wikipedia article that there are a lot of flats and sharps in the modal natural chords. And I was wondering if it's because they all refer to Ionian.

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So in Aeolian the "bIII" chord is read "take the 3rd chord from Ionian, and flatten its root; then use this flattened root and make a major chord from it since the roman numerals are capitalized". Does that sound right?

Borrowing chords from a parallel mode then is just a matter of picking chords from this table (I saw this video on modal interchange). So the resulting non-diatonic chord progression, for example I bVII IV bII, is still always in reference to Ionian (?). Meaning, bVII in this progression is read "take the 7th chord from Ionian, flatten its root, use it to make a major chord".

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    It's more accurate to use 'major' instead of 'Ionian' in your title. – Tim Jan 17 at 13:26
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Yes, you're correct! (One might say that it's actually relative to major instead of Ionian, but that's being pretty fussy.)

The only thing to watch out for is the accidentals that are "hidden" in some of the Roman numerals. Imagine you're in D and you want to add in the II chord that's borrowed from Lydian. There's no accidental with that II Roman numeral, so you might just think we have a regular supertonic chord in D. But remember that the ii chord is typically minor in major/Ionian, and this II chord is major, thus requiring a G♯. Another way to think of this is that Lydian has the raised fourth scale degree, which would again result in that G♯.

  • Or - hark back to D Lydian's parent - A major. Which contains that extra sharp - G#! – Tim Jan 17 at 13:23
  • Also, folks should keep in mind that some symbol conventions use upper case for any chord quality - like II for the minor supertonic triad in a major key. That mostly older convention can be confusing. – Michael Curtis Jan 17 at 19:01
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Consider, with modes of the major scale, that each is related to that major. Write them in a circle - each follows that circle, starting on a different note as it goes round.

Yours is one way to look at it; I prefer referencing the parent key. So, D Dorian, E Phrygian, F Lydian etc. all use the same chords as their parent key - C major. C Dorian, D Phrygian, Eb Lydian etc. all use the same chords as B♭ major.

Of course there are going to be lots of sharps and flats! There are in any altered notes! There's also lots of naturals, as they will be altered from the original sharps and flats!

That table may work for you, but I would instead be thinking along the lines (parallels) of G Ionian - G notes. G Dorian - F notes. G Phrygian - Eb notes. G Lydian - D notes. G Mixolydian - C notes, etc.

Reference tends to return to the major scale - that's the usual datum point.

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