With the dulcimer and modal tunings, you can play any tune using the same note relationship. A DAd tuning is a 1-5-8 relationship. The 1 is the first note of the scale (a D), the 5 is the 5th note of the scale (an A/as in DEF#GA) and the 8 is the octave higher d or the 8th note of the octave (DEF#GABC#d). Any other 1-5-8 tuning is played with the same tablature and fingering. CGc, AEa, GDg, EBe are the keys of C,A,G, and E in a 1-5-8 tuning. This tuning is commonly called Mixolydian mode, which isn't quite accurate as many Ionian mode tunes are played in this tuning as well.
I use a CGG which is an Ionian mode tuning. The note relationship of this tuning is 1-5-5 with the melody string being tuned to the same note that the middle string is tuned to. The scale starts at the third fret and I would use DAA tab not DAd. DAA, CGG, GDD, AEE, EBB are all 1-5-5 tunings in the Ionian mode (no half frets used).
A simple example of the difference in the two tunings is Brother John. In a 1-5-5 tuning, I'd play 3453, 3453, 567,567, 787653, 787653, 303, 303.
In a 1-5-8 tuning I'd play 0120, 0120, 234,234, 454320, 454320, 0-0middle-0, 0-0middle-0.
In either tuning (CGG, or CGc) I'd be playing exactly the same notes CDEC, CDEC, DEF, DEF, FGFEDC, FGFEDC, etc.
The only tunes that I can't play when tuned in CGG are true Mixolydian mode tunes with a flatted 7th note of the scale and are played on the 6th fret (NOT the 6+) in a 1-5-8 tuning. Old Joe Clark is an example of a true Mixolydian tune. It has to be played in a 1-5-8 tuning and uses the 6th fret. The only difference is between the Mixolydian scale and the Ionian scale is that one flatted note. That's why so many tunes are now tabbed in DAd, as you can play two different modes with the same tuning since most modern dulcimers have 6 and 6+ frets which gives you the correct note for either scale.
Charles E. Jones said:
Thanks. Are you able to play everything in CGC that you could play in DAD?
folkfan said: I'm with everyone else on this. For singing go lower. CGc would be only one step down from your DAd tuning, and does make for easier singing. I don't even tune up to D anymore as I always want to sing with my instrument. I'm in CGG or lower for everything.