Rebecca Martin’s jazz-tinged pop seduces in quiet ways. The singer/songwriter’s music is beautifully plain: her vocals are unmannered, and her acoustic guitar playing doesn’t call attention to itself. Martin’s sixth album, Twain, features a spare set of 12 originals and a cover of the Duke Ellington classic “Sophisticated Lady.” The well-known jazz bassist Larry Grenadier (Martin’s husband) plays throughout, and pianist Pete Rende (who also produced) and drummer Dan Rieser appear on a number of tracks. The opener, “To Up and Go,” sets the album’s tone: the song hums with an intimate emotional power that subtly pulls listeners in. “Beyond the Hillside” is stellar. The band’s accompaniment is understated, letting Martin’s voice and words work their magic. “Sophisticated Lady” starts with a solo by Grenadier before Martin joins in and the piece turns into a duet for bass and voice. “On a Rooftop” is a slice of striking pop brimming with rhythmic drive, melodicism, and appealing textures, while the excellent closer, “A Place in the Country,” has fine arco work from Grenadier.