Let’s say you want to shag a sexy British indie rocker. “Song One” not only instructs you on how to go about it (first tip: try to look like shagging said indie rocker is the last thing on your mind), but also suggests your lucky conquest could inspire the first track on his next album — though it helps to have a comatose brother, the way Anne Hathaway’s character does here. With its sensitive original score, true-chemistry central perfs and refreshing lack of irony, first-timer Kate Barker-Froyland’s low-key musical romance ought to send young emo crowds swooning en masse.

Perhaps the cleverest thing about Barker-Froyland’s delicately contrived debut is how uncontrived she manages to make it seem. A talented, good-looking kid (Ben Rosenfield) sings his heart out in the tunnels beneath Grand Central Station, only to be hit by a cab while crossing the street. Halfway around the world in Morocco, his more serious-minded sister Franny (Hathaway) is so absorbed in her anthropology studies that she hasn’t spoken to now-comatose Henry in six months.

The accident brings Franny home to New York, where she begins to familiarize herself with Henry’s life, hoping that a familiar sound or smell might revive him. She discovers a CD with his “Marble Song,” the first original composition Henry was proud enough to call his own, as well as a journal with clues pointing to his favorite singer, James Forester (up-and-coming actor-musician Johnny Flynn). Franny decides to attend one of James’ shows at the Bowery Ballroom, sticks around to explain the situation and, wouldn’t ya know, gets a pleasant surprise when he shows up at the hospital the next day with guitar in hand.

Everything that follows in “Song One” depends on what you make of James’ decision to stop by, bearing tea and sympathy. Against all odds, Barker-Froyland manages to sell this scene — a credit to both the grief-stricken authenticity Hathaway shows and the director’s own intuitively naturalistic style behind the camera. A significant talent in the making, Barker-Froyland earns our trust with almost imperceptibly handheld lensing and a welcome tendency to let shots linger long enough for the emotions to register.

But mostly, it’s the songs — by Jenny Lewis and Johnathan Rice of indie-rock duo Jenny and Johnny, with music help from Nathaniel Walcott — that makes it possible for this unassuming little drama to penetrate the cynical defenses of modern auds. Vaguely reminiscent of “Once,” another Sundance breakout that went on to find mainstream success (and eventually made its way to the Broadway stage, as this pic could conceivably do as well), “Song One” plays with the notion of two pitiful souls who meet at precisely the right moment to complement one another’s emotional needs.

Franny’s concerns are fairly self-evident, especially after she confesses how she’d berated her brother for planning to drop out of college and pursue his music. She needs a chance to atone for not taking his interests seriously (though one wonders how Henry might feel if he awakened to learn that she’d been shagging his idol).

In James’ case, the script presents him as an insecure poet and somewhat reluctant celebrity: He carries himself not like a star but as a sullen puppy, worrying aloud whether he will ever be able to overcome his creative block. It’s that ultimate naive-girl fantasy: a man who’s attentive, but also incomplete without you. In short, James needs a muse — preferably one with big Precious Moments eyes and uncannily good instincts about which Gotham music venues to hit on any given night.

SEE MORE: Anne Hathaway Talks About Her Nerve-Racking Sundance Premiere

So, while James tests out old and new songs on Franny, she reciprocates — with some encouragement from her embarrassment-be-damned mom (Mary Steenburgen, strong) — by singing back to him. Whereas Franny had shown zero interest in her brother’s passion for the past six months, now she finds music to be the most natural form of expression, attending concerts, buying vintage instruments and watching YouTube videos, each of which permit Barker-Froyland to squeeze more tunes into the film.

The story may be slight, but that leaves ample room to embellish with music, capturing a surprising range of styles (indie rock, blues, electronica) from the New York scene by way of texture. The film positively swells with songs, the lyrics of which have been attentively crafted to suit the emotions onscreen, especially when it comes to the pic’s eponymous number, “Silver Song.” While Hathaway earned her Oscar for live-singing last year, it is Flynn’s turn to impress with his heartfelt renditions of five original songs, at least one of which is sure to be heard at the Dolby Theatre next February.

Sundance Film Review: ‘Song One’

<p><strong>Reviewed at Sundance Film Festival (competing),</strong> Jan. 20, 2014. Running time: <strong>88 MIN.</strong></p>

  • Production: <p>A Worldview Entertainment presentation in association with Lotus Entertainment of a Marc Platt, Clinica Estetico, Playa production. (International sales: Lotus Entertainment, Santa Monica.) Produced by Platt, Jonathan Demme, Adam Shulman, Anne Hathaway, Christopher Woodrow, Molly Conners. Executive producers, Maria Cestone, Sarah E. Johnson, Hoyt David Morgan, Jacob Pechenik, Andy Neuberger, Bill Johnson, Jim Seibel, Kathryn Dean, Jared Leboff. Co-producer, Rocco Caruso.</p>
  • Crew: <p>Directed, written by Kate Barker-Froyland. Camera (color), John Guleserian; editor, Madeleine Gavin; music, Jenny Lewis, Johnathan Rice, Nathaniel Walcott; original songs, Lewis, Rice; music supervisors, Brian McNelis, Eric Craig; production designer, Jade Healy; art directors, Anne Allen Goelz, Brandon Conner Connolly; costume designer, Emma Potter; sound (Dolby Digital), Jeff Pullman; supervising sound editor, Paul Urmson; associate producers, Amanda Bowers, Thomas Froyland; special effects supervisor, Stephen Powers; visual effects supervisors, Luke DiTommaso, Chris Healer; visual effects, The Molecule; assistant director, Josh Newport; casting, Bernard Telsey, Tiffany Little Canfield. </p>
  • With: <p>Anne Hathaway, Johnny Flynn, Mary Steenburgen, Ben Rosenfield, Lola Kirke, Cass Dillon, Paul Whitty, Elizabeth Ziman, Sharon Van Etten, Dan Deacon, the Felice Brothers, Naomi Shelton.</p>