Her megahits show off her voice's airy, nimble side, but Olivia Newton-John's instrument can also pack a wallop when a song calls for it. “Toughen Up” is a slinky rocker with an exclamatory chorus; “Weightless” is commanding electropop. Newton-John also flexes her power with confident covers of musical-theater standards like the Webber/Rice barnburner “Don't Cry for Me Argentina” (from Evita) and Sondheim's “Send In the Clowns.”