Joni used some fairly unusual tunings, as she learned dulcimer intuitively (no surprise, as she was self-taught on guitar as well). Back when she started recording with it, it was a fairly esoteric instrument in mainstream contemporary folk--Force & D'Ossché ("In Search of the Wild Dulcimer") were pioneers in taking it out of the Ionian (DAA) mode in which Richard Fariña discovered it; most other prominent players at the time had grown up "in the tradition," either Appalachian or Celtic. (A few are still with us, thank heaven). I am surprised to see she used a tuning as conventional as the inverse Mixolydian (which David Massengill later intuited and made his hallmark) for "A Case of You." which (along with "Carey") I'd always played and taught in standard Mixolydian (low to high: DAD). Leave it to her to place the bass string in the middle! (IIRC, Massengiil strings his dulcimers conventionally despite inverting the tuning). I've also used DAD for "California," which leads to a bit of fudging with one-finger barre chords that simplify some inversions and sacrifice some additions & suspensions. To play "All I Want" in DAD meant playing in the key of G, using some partials and even letting the vocal alone carry some of the notes. Now that I've seen her unusual tuning (could've sworn that the transcriptions in the companion songbook for "Hits"--or was it for "Misses?"--had her using the all-one-pitch variant of Galax tuning, in F#), I'm going to try and master it for an upcoming tribute showcase gig in August--which means (sigh) bringing two dulcimers so as not to kill time onstage retuning.   Then again, I just bought a chromatic dulcimer, so anything could happen.....