Esperanza Spalding certainly has got the world on a bass string these days. With a fresh sound and a fearlessness to match her considerable gift, she continues to turn up on a wide array of artists’ CDs contributing bright-spot guest vocals and bass. Fittingly, Spalding is no less audacious in her solo career. For her third solo outing she indulges her “acoustic chamber music side,” with inspired, intimate results. Centered on Esperanza’s winsome-yet-wise vocals, plucky upright, and a Gil Goldstein-arranged string ensemble, the 11-track disc launches with the lyrical lullaby “Little Fly.” “Knowledge of Good and Evil” broadens the soundscape with bold bowed and pizzicato strings, and Terri Lyne Carrington’s lilting drum backbeat, which elicit flowing scat and bass solos from Spalding. Gathering more steam, “Really Very Small” rides a rolling McCoy Tyner-esque bass line that Esperanza effortlessly dispatches while singing—her compositional flair for conceiving bass and lead melodies at the same time firmly intact. Taking a South American turn, pianist Leo Genovese’s “Chacarera” recalls Cachao’s folk/classical wellsprings; the rich, rubato ballad, “Apple Blossom” features a vocal duet with Milton Nascimento; and a sparse-but sparkling cover of Jobim’s “Inútil Paisagem” pairs Spalding with vocalist Gretchen Parlato. Elsewhere, Esperanza’s angular vocal melody on “Winter Sun” melts away for her best bass solo turn, all driven by Carrington’s funky feel. “Wild is the Wind” builds from ballad to gale force, while “What a Friend” climbs to a pitched peak and has a quality descent. What’s next for Esperanza? Who knows? But we’re paying attention.