i use dadgad and standard tuning both. usually for different things.dadgad is difficult for sessuin backing--but then i usually play a mandolin, or bouzouki at a sessuin, however a friend of mine used to play dadgbd--two dropped ds for sessuin backing. you get regular chords in the middle four strings and two drones for d or g which reduces the capo needs--he rarely uses one. i almost never use a capo either.

with dadgbd you only have to tune up the high d to e and you get dropped d when wanted or tune the b down to a for dadgad. however he is a fantastic guitarist--he sounds great playing anything.he recorded a smithsonian folklore album in the sixties and toured with john lee hooker.

i used to also play several open c tunings and open d, both are great for certain songs. on a strong guitar those low c notes resonate like crazy. and yeah joni mitchell used many many tunings. she is a genius . she even played revolutionary dulcimer music--for the time