Nanohedron wrote:I can speak of a note in terms of number, but once we start in on Aeolian or Dorian modes, or the different types of minor scales, I'm pretty well sunk.
So let's take a D whistle, take off our fingers one by one and keep going till we reach our starting point an octave up...
D to D is major, and we all know that.
E to E is Dorian, which is like natural minor with a sharp 6th (the C#).
A to A is Mixolydian, which is like major with a flat 7th (the G nat).
B to B is Aeolian, which is sometimes called natural minor. It's the sharpening of the 7th from A nat to A# that makes it truly minor and gives rise to the alternative melodic and harmonic minor scales, which probably aren't that relevant to much true trad.
For trad purposes, you can probably pretty well ignore Lydian (G to G, or major with a sharp 4th) and certainly ignore Phrygian (F# to F#) and Locrian (C# to C#).
What's interesting to me is the harmonic implications of staying truly within a mode...
E Dorian should logically have a I, IV, V primary chord set of Em, A (note the major chord IV where E minor would have Am) and Bm, but will very often want D as a kind of alternative dominant.
A Mix should logically have A, D and Em (minor chord V where A major would have E), but many nominally A mix tunes will work as well or better with E.
B Aeolian should logically have Bm, Em and F#m (minor chord V where B minor would have F#), but probably not cry out for A as strongly as E Dorian asks for D.
The moment you start using B instead of Bm as chord V for E Dorian or F# instead of F#m as chord V for B Aeolian, I'd say you're pushing that tune out of mode and into the minor. But perhaps there's less risk of this in E Dorian when that alternative dominant D chord's usually pretty obvious, whereas Aeolian tunes are maybe more vulnerable? But then again you have to hack Mairi Bhan Og to fit a major V!
[Edited to correct the B Aeolian bit, where I had 'probably not cry out for G' because I was thinking of A Aeolian to match a white-note C major/Ionian context instead of my whistle-based D starting point.]