Terrence J. Nolen may well be Philadelphia’s most inventive director of musicals. His intimate, immersive production of Once, on the F. Otto Haas Stage through Oct. 28, transmutes this 2012 Tony Award-winning show’s modest pleasures into a stirringly beautiful entertainment.

Scenic designer David P. Gordon envelops the audience, seated in the round, in a gritty Dublin of graffiti-covered walls and neon pub signs, with shadowy lighting by Thom Weaver. The performance begins with a prologue, a medley of Irish tunes performed by what seems like a motley group of street musicians (costumed by Olivera Gajic).

They assume different guises during the show, transforming into a backup band and various supporting characters, invading the aisles, and tackling some 30 instruments with aplomb. There’s even a superb little-girl fiddler (8-year-old Lučia Brady), who happens to have played Carnegie Hall.

The idea of metamorphosis pervades this staging. Music is the primary agent of change, helping a lovelorn Dublin busker and vacuum cleaner repairman known as Guy (Ken Allen Neely) express his feelings and find his calling. Serving as a catalyst is Girl (Katherine Fried), a Czech immigrant who buoys him with her unrelenting, if sometimes irritating, optimism and energy.

Their lives quickly intertwine, and the tender and passionate music he’s written for and about his ex-girlfriend – especially the Oscar-winning “Falling Slowly” – becomes the anthem of their fragile new romance.

Once has its own history of metamorphosis. The stage musical, with a book by the playwright Enda Walsh and music and lyrics by Glen Hansard and Markéta Irglová, is based on a successful 2007 independent film of the same title.

The film, in turn, was loosely based on the real-life relationship – both musical and romantic – of the Dublin-born Hansard and the Czech Irglová. They starred in the film (written and directed by John Carney) as fictional versions of themselves, drawing on their considerable charm and chemistry, improvising scenes, and performing their own music. That gave the undertaking an authenticity that is tough to equal.  

At the Arden, Neely – lanky, handsome, melancholic and sweet-voiced – is well-cast as Guy. Fried, as Girl, plays the piano and sings her principal numbers, the seductive “If You Want Me” and the haunting “The Hill,” with brio and tenderness. Their chemistry doesn’t seem overpowering, but even that may be OK – if we’re to believe that their friendship and mutual love of music are what matter most in the end.

Among the fine ensemble, the standout (no surprise) is Arden favorite Scott Greer, who is almost unrecognizable and very funny as Billy, the half-Spanish music-store owner who drinks Rioja, dances the tango (Steve Pacek choreographs), and would, in a different musical, be a more threatening competitor for Girl’s heart. Greg Wood, another Philadelphia stalwart, has a small, poignant role as Da, Guy’s widowed father.

There’s a delicacy of feeling in Once that, for my money, didn’t translate well in a large Broadway theater. In the compact confines of the Arden, Nolen and company have made this spare, little musical unexpectedly lush and entrancing.

Theatre

Once

    • Through Oct. 28 by the Arden Theatre Company, 40 N. 2d Street. Tickets: $37-$52. Information: 215-922-1122 or www.ardentheatre.org.