A movie musical not based on existing source material is rarer than it might seem in 2016, viewed by most major Hollywood studios as a costly gamble not worth taking. Director Damien Chazelle (2014's "Whiplash") has not only defied the odds with Lionsgate's "La La Land," but has hit a swirlingly incandescent high note. Giddily ambitious but perhaps more bittersweet than some will be expecting, this melodic love story proves fanciful but rooted, emotionally, in a reality where happily ever afters are not certainties. As its two lead characters, played with heart-on-sleeve grace by Emma Stone (2015's "Aloha") and Ryan Gosling (2016's "The Nice Guys"), navigate the excitement of a new relationship, it is only a matter of time before the messiness of real life gets in the way. Chazelle and his actors make every success and pitfall dramatically involving and honest, backed by a lovely soundtrack of original tunes composed and orchestrated by Justin Hurwitz. The film's only disappointment is that there aren't more of them.

Work-for-hire jazz pianist Sebastian Wilder (Ryan Gosling) and aspiring actress Mia Dolan (Emma Stone) are two twinkling stars out of millions struggling to fulfill their dreams in modern-day Los Angeles. Sebastian, who hopes to one day open his own club, dies a little more inside every time he takes a gig he doesn't believe in, while Mia has grown weary of a string of failed auditions. Their initial two run-ins—the first during a traffic jam, the second at a bar where Sebastian is singing Christmas carols—are contentious, but then something surprising happens when they properly meet a third time at an afternoon pool party in the Hollywood Hills: they kinda-sorta hit it off. A sweeping romance is born, but will it be able to survive as their own aspirations and career paths threaten to take them down opposite paths?

With unmistakable shades of Jacques Demy's "The Umbrellas of Cherbourg" and "The Young Girls of Rochefort" written into its DNA, "La La Land" imagines a reality where singing and dancing is as natural as breathing. Cinematographer Linus Sandgren (2012's "Promised Land") proves unencumbered by the rules of conventional lensing, his camera swooping, gliding and even taking flight while observing the characters (who, in one scene set at Griffith Observatory, also defy gravity). The opening number, "Another Day of Sun," is an eye-popping technical wonder, achieved in what appears to be a single shot as Los Angelenos stuck in traffic stretch their legs and exercise their vocal chords on the backed-up I-110/I-105 Interchange. As day duskily transitions to evening, the quixotic "A Lovely Night" finds Mia and Sebastian sharing their first flirtations at a Hollywood Hills overlook. Also lovely: "City of Stars," first sung—too briefly—by Sebastian on a Santa Monica boardwalk, and later as a touching duet reprise with Mia.

Anyone who saw 2011's "Crazy, Stupid, Love." will already be fully aware of the onscreen chemistry between Emma Stone and Ryan Gosling, making their casting as Mia and Sebastian exceedingly ideal (it doesn't hurt that they can ably carry a tune). The connection Mia and Sebastian share leaves them light on their feet, as new romances are apt to do, but their relationship is not exactly care-free, the complicated struggles in their professional lives placing a wedge in their happiness. Stone gets several especially juicy moments in the spotlight, none more so than her show-stopping eleventh-hour ballad "Audition (Fools Who Dream)," so purely and powerfully performed it could very well earn her rapturous awards notice like "And I Am Telling You I'm Not Going" did for Jennifer Hudson in 2006's "Dreamgirls" and "I Dreamed a Dream" did for Anne Hathaway in 2012's "Les Misérables." Mia's pro-active courage in creating her own one-woman show is a welcome detail, and Stone beautifully finds equal parts strength and vulnerability in a character who, even as she risks failure, isn't simply going to wait for jobs to come her way.

"La La Land" tells a familiar story in a fresh way, its harmonic tapestry a throwback to the glitzy musicals of the 1940s and '50s. Justin Hurwitz's original songs, with lyrics by Benj Pasek and Justin Paul, transfix just as they should. An additional couple tunes, in fact, could have transformed an already-great movie into an even better one; there are occasional stretches without music that slow down the pacing and rhythm of what surrounds them. Make no mistake, though; a film running two-plus hours that leaves the viewer craving more is doing something very right. Elevating the plot's poignant trajectory is one key question: Is Mia and Sebastian's a forever kind of love? Director Damien Chazelle does not sugarcoat the truth of his story, using the gift of song as a dramatic expression far more resounding than the spoken word possibly could. The final scenes, taking the audience through a whirlwind "what-if?" scenario, ache for what could have been but isn't while uplifting for what is and ultimately should be. The luminous "La La Land" is wise enough to recognize the difference.