Thunder rumbles. Lightning flashes. A rope slithers on, cordoning the ensemble in the shape of a ship's hull as a sail rises behind them. Wind squalls. Other actors become waves and seaweed. Two bodies, both all in white, float above the others. They're reaching fruitlessly for each other's hands. Wordlessly and gorgeously, San Francisco Playhouse's "Twelfth Night" communicates the backstory of twins Viola (Sophia Introna) and Sebastian (Bear Manescalchi), who are separated by a shipwreck. Then Shaina Taub's music kicks in, a joyful, jazzy expansion of the show's famous first line: "If music be the food of love, play on." This production, which opened Wednesday, Dec. 1, is no ordinary take on William Shakespeare's romantic comedy of gender swaps, mistaken identities and interlocking love triangles (which grow into quadrilaterals). Conceived by Kwame Kwei-Armah and Taub, it adapts Shakespeare into a musical so persuasively that you might think the two genres had always been intertwined. Is there really that much difference, after all, between a searching soliloquy and an 11 o'clock number? San Francisco Playhouse is a midsize company, but it's still a scrappy one — the kind of place where the founders' dog roams lobby and house on opening night. With "Twelfth Night," director Susi Damilano reveals it at its best, showing how much artists can accomplish when they don't have Broadway budgets, but more than make up for it with ingenuity, craft, perceptiveness and compassion. The show's whole setup — castaway Viola disguising herself as Cesario in order to work for Illyria's Duke Orsino (Sean Fenton) — is dispatched before you know it, within a single, economical number and costume change. Shakespeare newbies are welcome here; the pro Michael Gene Sullivan as Sir Toby Belch can tell a whole story the way he enters falling down a staircase, the way he uses single words as rocket launching pads to whole new shades of meaning. Damilano has assembled a cast with stellar singing voices, which under the music direction of Dave Dobrusky blend together as if they'd been in a chorus together for years. Especially strong is Sam Paley as Feste, who approaches the ballad "If You Were My Beloved" as if she could lift the burdens of thwarted lovers Viola and Orsino off their shoulders.