Few musicians have transformed their art as often and as thoroughly as Tim Buckley did between 1966 and 1975, when his brief career ended with his untimely death at 28. He quickly veered from ethereal folk-rock singer to wildly exploratory vocal improviser to funky blue-eyed soul man, with many fascinating twists and turns in between. Two weeks ago the excellent Tompkins Square label released a live solo set from March 1967 that captures Buckley in the middle of one of those transitions; it was recorded at New York’s legendary Folklore Center, a small performance space owned by Izzy Young and located above a folk-music store, in front of an audience of about 35.