Laurent wrote " 1 track out of the Blue era: California where Joni plays lap steel. I had no idea all these years that Joni used a lap steel for this. Although when I watched it was right on. I assume it's in open tuning? So my question is: in what other songs, from Blue or else, has Joni played an instrument other than guitar, piano or cigarette machine?"
As far as I know, Joni played the dulcimer on All I Want, Carey, California and A Case of You, all from Blue, of course. That has been widely documented, and she discussed the origins of her instrument on more than one occasion captured for posterity. Bob Sart
