DAA or DAD as primary tuning ?
General mountain dulcimer or music discussions
"the vast majority of those Mixolydian tune book songs are not Mixolydian modal songs. They are Ionian Mode songs being played in Mixolydian DAd using the 6+ fret."
This is correct - or you could play across the strings and use the 2nd fret of the middle string.
This shows the confusion created by calling tunings by mode/scale names. Think of the modes as scales and scale variations. Ionian mode is a fancy name for the major scale, the old do re mi... Myxolydian is a fancy name for the major scale with the 7th note flatted. (Aeolian and Dorian are fancy names for two kinds of minor scales.)
On most modern dulcimers (w a 6.5 fret):
When tuned DAD you play an ionian/major scale from 0 (open) to the 7th fret using the 6.5 fret and skipping the 6th fret.
When tuned DAD you play a myxolydian/flat-7 scale from 0 to 7th fret using the 6th fret and skipping the 6.5 fret.
DAD tuning was called "myxolydian" because on the original dulcimers - with NO 6.5 fret - it is the only scale you could get going from open to the 7th. Also, that's how you MUST tune the dulcimer to play a song like Old Joe Clark that uses a flat 7th (on 'Clark': 4 - 5 - 6 - 5 - 4 - 3 - 2...)
To play an ionian/major scale on a trad dulcimer - with no extra frets - you MUST tune to DAA, and the scale starts with the D that's now at the 3rd fret, and you play 3 - 10 on the frets. If you tune DAA on a modern dulcimer, you still play 3 - 10 for the major scale, but you have to make sure to skip the 6.5.
That's why DAA tuning became called "Ionian" - b/c that's the way you have to tune to get a major/ionian scale on a traditionally fretted dulcimer.
With the 6.5 fret (or playing across the strings) you can find the pure major scale songs even if you're in DAD tuning.
Bottom line: It's NOT really the tuning that is "myxolydian" - it's that that tuning allows you to play the myxolydian scale, in particular on a dulcimer with no extra frets. Same with all the other Greek names.
I tend to stay in DAD because I can play either mode with no retuning. However, you can't play a D-myxolydian scale on a dulcimer tuned DAA - unless you use the bass string.
I think of the DAD tuning as 'containing' the DAA within it - on that middle, A, string - but not vice versa.
Hope that makes sense. It can be a little confusing!