In 2003, just as her career started to bloom, the whisper-toned jazz singer Jane Monheit sang on three songs for Mark O'Connor's In Full Swing, a fiddle-led jazz romp that also featured Wynton Marsalis. Since then, Monheit has become one of the world's most respected soft singers, her voice lighting upon words like a diaphanous butterfly upon a flower's open blossom. Saturday, she returns the favor by giving O'Connor—a leading bluegrass, classical and jazz instrumentalist— the opening slot. Expect smoldering stage-sharing. SATURDAY, FEB. 2, AT CAROLINA THEATRE. $32–$57/8 p.m.