Who or what is the MVP of "Sing Street"?

Sing Street, the latest film from our most musician obsessed auteur John Carney, has been expanding with more theaters each week at a fairly strong clip. Six weeks in, there's no expansion (a very crowded weekend) but its fanbase keeps growing exponentially as more people "discover" it. Like Carney's previous music-based indies, the Oscar winning, transcendently low-fi Once and the more mainstream but surprisingly rewatchable Begin Again, whatever you might want to say about Sing Street an adjective that could safely and accurately describe all three films is "endearing"...