From its first shot, musical romantic drama Once announces its modest means of production: a camera films a man (Glen Hansard) busking on the other side of a busy road, a shot laced with the telltale shakes from operating a handheld camcorder. From the lossy DV cinematography to the ordinary shot setup, the microbudget filmmaking on display is instantly clear from this opening alone. Yet, by immediately calling attention to its DIY aesthetic, Once primes its audience for the tenderly muted nature of the romance at the film’s heart.

Like the means of its production, John Carney’s breakthrough indie darling Once – celebrating its 15th anniversary – is quietly unassuming in its depiction of unacted-upon love amid musical bonds. Its protagonists are unnamed (credited only as Guy and Girl), portrayed by non-actors (Hansard and Markéta Irglová, in her only narrative film credit), and uneventfully part ways at the end of the movie rather than consummating their mutual attraction for one another. Despite being a cinematic musical, the film continuously sidesteps the oft-heightened nature of other movies in its genre: its songs are all performed organically in the film’s diegesis, its arrangements are mostly spare and minimal, and there’s often little to the onscreen action other than the act of performance. Rather than visually embellish its musical numbers, Once steadfastly adheres to its down-to-earth style to reflect its music’s capacity for expression on its own and how its characters use that music to say what they’re otherwise unable to tell each other.

Much of the pleasure in watching Once comes from Carney’s understanding that nothing does Hansard and Irglová’s songs justice quite like presenting them exactly as they are without dressing them up. The film’s signature number, the underdog Oscar-winner “Falling Slowly,” is shot as plainly as can be, showing the two musicians experiencing the intimacy in sharing a song together for the first time. This mindset extends to the rest of the film as well, from the rudimentary tracking shots of “If You Want Me” mirroring the musical introspection of a nighttime walk, to the use of a faux home movie montage embodying the lingering memories of an ex on “Lies.”

The movie’s unshowy nature extends right down to the very means of its filming – making optimal use of the relatively inexpensive Sony HVR-Z1E digital camera rather than industry-standard film cameras. Carney and Hansard, agreeing in pre-production to keep the film as low-budget as possible, chose to bring additional veracity by shooting in public spaces around Dublin, capturing the busiest periods at Grafton Street and the quiet intimacy of a mostly empty midday bus as only filming on location could.

Cinematographer Tim Fleming’s use of long lenses to stealthily shoot from afar amid crowds of people yielded an additional layer of authenticity as well: allowing the non-actors at the core of the film to let down their guard and improvise, lending their performances all the more naturalism. The charm in watching Hansard and Irglová bond over the runtime without strictly adhering to a script is palpable, the chemistry between the two achingly present even if viewers don’t know that they briefly became a couple after filming.

It’s particularly endearing to see the compounding effect of the film’s deliberate technical limitations in action. The combination of the slightly unsteady handheld camerawork with Carney and Fleming’s choice to only use natural light – even in night scenes lit only by street and porch lights – gives every sequence the impression of a small scrappy team earnestly making the most out of what little they’re working with. The film spends so much time acclimating the viewer to its style that its single climactic break from that – implementing crane shots in its final montage – feels all the more earned for how the crew holds off on this sweeping gesture until the most opportune time.

As a result, the prevailing allure of Once comes not from seeing how the next musical number will be staged or shot, but in the compulsion of seeing how this brief encounter between the Guy and Girl further develops with each song. By the time that the film arrives at its most spare number – Irglová’s mournful solo piano ballad “The Hill,” performed in the minimal somber dim blue lighting of an empty rehearsal space – the piercing impact of the songs-first approach reaches its pinnacle. With unadorned cinematography, the nakedly emotional lyricism of the song becomes the primary focal point, one where the Girl can vent her torn romantic feelings that she normally keeps guarded. In the stillness of this scene, the song’s abrupt ending, suddenly cut short when the Girl chokes up while singing and breaks down in tears, becomes all the more haunting.

However, if one had to pick only one moment that best encompasses the strengths of Once’s ramshackle production, there’s no better choice than a muted scene between Hansard and Irglová late in the film. The two take a trip out to the countryside, where Guy asks Girl whether she loves her absent husband with whom she plans on reconciling. In an unscripted line of unsubtitled Czech, Irglová responds that Hansard’s character is the one she loves, which produces genuine confusion from Hansard – unaware of what Irglová says.

The moment is a perfect bit of acting serendipity, not only because it’s an exchange that may not have been produced under a bigger production, but because it proves how letting Irglová and Hansard live fully within these roles elicits snapshots that feel especially real. Like the film itself and the unspoken romance at the center of it, Once’s DIY ethos creates quiet wonders in the fleeting, showing how much can carry a film if the right spark is there and the passion is present no matter how small the budget. Nothing else could speak truer to the expressive power of two musicians spilling their deepest feelings into the songs they create together.