LENOX — Musical theater, oscillating between repertory and innovation, demands its performers be polytropic: operetta-like legit sounds, jazz vernacular, pop casualness. The brilliance of Audra McDonald, who dropped by Tanglewood’s Ozawa Hall for a solo recital Sunday night, is not just her ability to move through those styles, but that one never notices the change of channel. Audra McDonald - Jazz - Tanglewood - Idina Menzel - Music