Go figure: one of the great underappreciated singers of the 2000s funk/soul revival’s early wave was an American ex-pat Brooklyn native cutting records in Helsinki. Nicole Willis’s turn in the mid ’90s acid jazz ensemble Repercussions sent her off into an unpredictable run of slept-on psychedelic R&B throwbacks, with Keep Reachin’ Up, the first record she cut with the Soul Investigators in this anything-old-can-sound-new-again mode, as a stunning (re)arrival. The Curtom-funk pump-up of “Feeling Free,” the cognac-hazed, langourous string flourishes of early ’60s breakup vibe “No One’s Gonna Love You,” and the sophisticated strut of Pam Grier flick-worthy “Blues Downtown” make fine accompaniment for her voice’s ability to soar, punch, coo, and seethe with the best of them.