In her written introduction to Sweet Home (Random Chance), young vocalist Pyeng Threadgill rather boldly refers to herself as “the instrument for bringing the music of Robert Johnson into the 21st Century.” Which may be news to guitar genius (and diehard blues devotee) Eric Clapton, whose own tribute to the legendary Mississippi bluesman has been riding the charts most of the summer. Clapton, smart enough to appreciate that it takes a lifetime of joy and pain to invest Johnson’s songs with the hard-won wisdom they require, wisely waited until he was 59 to deliver Me and Mr. Johnson. Threadgill, daughter of celebrated composer and multi-instrumentalist Henry Threadgill, is less than half Clapton’s age. And it shows. She has a glorious voice, sweet and smooth as apple butter, and has a firm intellectual grasp on Johnson’s sociological themes. Emotionally, though, there’s significant disconnect. Her renditions of “Dead Shrimp,” “Sweet Home Chicago,” “When You Got a Good Friend” and eight other Johnson classics are gorgeous. But, apart from a “Come on in My Kitchen” that sizzles with seductive spirituality, they’re lacking the requisite belly fire. Better to leave the heavy lifting to Clapton. Better yet to go whole hog and get Legacy’s 41-track, two-disc compilation of Johnson’s own Complete Recordings.