If not for the trees rustling in the night air behind the stage; if not for the late-arriving nutcase, two seats over, twitching as he fumbled through his knapsack; if not for the occasional helicopter whirring overhead, distracting the eye from Rosario Dawson’s heaving dulce de leche bosom, it would have been hard to believe that this – this surging, exuberant, whimsical, astonishingly fresh musical – was Shakespeare in the Park. So what if the show was actually 34 years old? In the Public Theater’s 50th-anniversary season, this new production of “Two Gentlemen of Verona” reminds us why the institution still matters.

John Guare and Mel Shapiro’s witty, fast-paced musical adaptation of Shakespeare’s “Two Gentlemen of Verona” first appeared at the Delacorte back in 1971, the same year the Coca-Cola Company convened a scrappy bunch of smiling, vacant-eyed flower children on a hillside in Italy and had them sing “I’d like to buy the world a home, / And furnish it with love, / Grow apple trees and honey bees, / And snow white turtle doves.”

As the production at the park opens (after a fanfare of birdcalls), a pudgy bearded cherub in John Lennon glasses, a rippling water spaniel-style wig, and a filmy toga (the droll and deadpan Don Stephenson, who later doubles as a bad guy) trills a hymn to love in the dulcet notes of Tiny Tim. He makes “Spamalot’s” Prince Herbert seem macho. His solo melts into an opening sequence in which joyful, dancing renaissance-era Italian hippies in flowy peasant togs sing “Love Reminds Me of Me.” It could be a reprise of the Coke ad … if the singers had chugged a magnum of Red Bull before beginning their warbling.

Neither Coca-Cola nor Red Bull had hit Stratford-upon-Avon at the turn of the 16th century, when this tale was written, but love, turtledoves, and keeping company are the stock in trade of “Two Gents.” (In one of the many instances of brilliant staging in the show, a dove on a wire glides down to the stage to receive a love letter.) The play is one of Shakespeare’s slightest, and earliest: In it, the fickle Proteus and his true-blue friend Valentine fall in love with two women, Julia and Silvia (actually, callow Proteus falls for both of them).

But Messrs. Guare and Shapiro amplified the show’s attractions through nontraditional casting. To them, Silvia – she whom all the swains commend – was an empowered African-American Amazon, as amoral as a tomcat and as vivacious and touchable as a kitten. Valentine was black, too; Julia and Proteus were Latino; and the music, written by Galt MacDermot (who composed the score to “Hair”) had a Caribbean and R &B flavor. Theatrical asides were as likely to be in Spanish as in English.

With their “Dos Amigos” update of “Two Gents,” the creative team didn’t merely bring Shakespeare back home; they brought him to the barrio. At the time, this was groundbreaking. It still feels that way. The Delacorte buzzed with a sense of occasion on the night I saw it, as the audience registered its good fortune: A real musical was under way, not an ironic meta-musical that gets laughs by mocking its form, but a saucy romp that takes delight in telling a (fairly) straightforward love story.

This raises the question: Where did “Two Gents” disappear to, these last three decades? The show was a smash hit when it first opened at the Delacorte and quickly jumped to Broadway, where it won the Tony for Best Musical in 1972, unseating “Grease.” But then it left town, and only now is back. What happened? Were its fans so stoned on hash brownies when they saw it that they forgot it had existed? Or did the show accidentally tumble into the 1970s squeam trunk – along with bell bottoms, shag rugs, the color orange – becoming something to be blushed over, denied, stashed in the attic until fate re-anointed it hip? If so, then along with bell bottoms, shag rugs, and orange, “Two Gents” is back.

What makes this production sing (and dance), apart from the song and story, and golden girl Kathleen Marshall’s surefire direction and buoyant choreography, is its trio of star performers. The richly talented newcomer Oscar Isaac gives a pouting, cavorting portrayal of fatuous Proteus that makes Pippin look deep in comparison; he also has a gift for accents and funny inflections. (Raul Julia originated the role.) Renee Elise Goldsberry, as Silvia, is a sinuous, petulant powerhouse whose lust for life electrifies her numbers. Her chemistry with her leading man, Norm Lewis (Valentine), lends suspense to their funny, sexy scenes. Mr. Lewis is a rare actor, possessed of a wide-ranging, molten voice that casts a spell – you want to hear him singing baritone ballads like “O Holy Night,” or “Do Nothing ‘Til You Hear From Me” – but he also projects a curious (and very 1970s) quality of decency and humility.

As Julia, Rosario Dawson makes her stage debut here. She can’t act at the level of her colleagues, but she is not miscast, if only because she’s so lovely – can you miscast a rose? She gets the beauty-is-its-own-excuse-for-being exemption. Like their predecessors, these stars are Latino and black. The rest of the company is nimble and engaging – especially the hunky Paolo Montalban, as Eglamour (one of Silvia’s raft of lovers); Megan Lawrence, playing Silvia’s maid Lucetta, in her solo, “Land of Betrayal”; and Mel Johnson Jr., who plays a warmongering Mobutu Sese Seko-style Milanese dictator, and whose chilling stump-speech song, “Bring All the Boys Back Home,” elicits a wave of sympathetic reaction from the war-conscious crowd.

All this makes “Two Gents” seem surprisingly timeless – or, perhaps, we have simply returned back to the moment its time capsule occupies. In any case, catch it if you can, and pray they bring it back to Broadway, where it should be a shoo-in, or love-in, for best revival.

Central Park (82nd Street entrance, 212-539-8500).