When the cheery new Roman Holiday musical made its San Francisco debut in June, I noted that this out-of-town tryout destined for Broadway was part of a trend of mid-century nostalgia that's been going on in Broadway theater for a decade or so, from jukebox-style creations like Jersey Boys and Beautiful: The Carole King Musical, to more sumptuous stuff like the recent revival of The King and I. This is, after all, because Baby Boomers are now the primary audiences for Broadway shows, and they eat this stuff up like nobody's business. Perhaps the most ambitious and successful of these throwback confections in recent years is the Tony Award-winning An American In Paris, a new adaptation based on Vincente Minnelli's 1951 musical film, which itself was inspired by the 1928 orchestral piece of the same name by George Gershwin.

The Oscar-winning film came about in part because Gershwin's lyricist brother Ira Gershwin suggested it as an idea to producer Arthur Freed, and it included several popular songs by the Gershwins like "I Got Rhythm," "Nice Work If You Can Get It," and " 'S Wonderful" — all sung and danced by Gene Kelly and Leslie Caron, with Kelly also choreographing, and the film ended with a 17-minute ballet sequence set to the orchestral piece that itself cost a record-setting $450,000 to produce.

The new production, which has been on tour since last fall and opened at SF's Orpheum Theater on Wednesday, arrives fully polished from months on the road, in its straight-from-Broadway form, with Tony Award-winning sets by Bob Crowley, Tony Award-winning orchestration by Christopher Austin, Don Sebesky, and Bill Elliott, and incredibly complex, beautiful choreography by Chistopher Wheeldon, which also took home a Tony Award in 2015.

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Make no mistake: This is as much a modern ballet as it is a musical, and the excellent ensemble in An American in Paris works hard throughout the show's two and a half hours and sixteen musical numbers. That makes this show a dream come true for lovers of dance, and a bit of a lengthy slog for people who like their musicals to hop along with more words and comedy to break up the music and the toe-tapping. There, are in fact, several pieces of the plot that play out purely in dance — and like the original film, the show ends with a wordless 20-minute ballet sequence. In between there are some extra Gershwin songs that weren't in the film, and there is plenty of comedy, but the pacing may strike some as pretty dated (i.e. slow).

The strongest dancer in the cast is ballerina and lead actress Sara Esty, who plays the role of Lise — and in her wide-eyed moments bears a striking resemblance to Fellini muse Giulietta Masina. Esty, a former soloist with the Miami City Ballet, understudied the role on Broadway and has been on tour ever since, and she turns out to be a beautiful singer and captivating actress as well, making her this cast's bonafide triple threat.

Also a beautiful dancer and strong singer, though perhaps a bit over-earnest acting-wise, is her co-lead McGee Maddox as Jerry Mulligan. The role is a challenging one in that it veers from golly-gosh soldier fresh from the war, to earnest artist, to moonstruck lover, to prolific dancer — and filling shoes once filled by the great Gene Kelly is a lot to ask any young performer.

Rounding out the cast is the incredibly likable Stephen Brower as narrator and Gershwin stand-in Adam Hochberg, the very funny and commanding Emily Ferranti as wealthy arts patron Milo Davenport, and the talented and handsome Nick Spangler (whom Amazing Race fans will remember as the winner, with his sister Starr, of Season 13) as Henri Baurel — who gets to shine in a grand, surprise tap number in Act 2 that I won't spoil here.

The sets, with the addition of projections and Tony-winning lighting design by Natasha Katz, are beautiful in themselves, and do an especially good job of evoking the salons of Paris of the last century.

It isn't a requirement that you be a Gershwin fan and a ballet fan to appreciate the major undertaking of this production, but it will likely aid in your enjoyment of something that is, above all, squarely aimed at nostalgia for an era of musicals that barely exists anymore. It also succeeds in many ways that Roman Holiday did not — the music, while not all original to the movie's plot, all dovetails nicely into the story and doesn't feel shoehorned in places it doesn't belong (with the possible exception of "Fidgety Feet" in Act 2). It's an old-fashioned, star-crossed love story with plenty of pretty flourishes, but Book of Mormon this is not.

An American in Paris plays through October 8 at the Orpheum. Find tickets here or daily rush tickets through the Today Tix app.

McGee Maddox and Sara Esty in 'An American in Paris.' Photo: Matthew Murphy