…Upon a time is NOT the theme of this movie. My sister introduced me to it, and I really, really love it!
The basic storyline is guy, girl, he busks, she meets him, they end up playing music together, they get a band, record an album, and then all go their seperate ways. Kind of thing.
One thing I really liked about it was that it had the Napoleon Dynamite style hand-held cameras, and the fact that the only music was played by the actors, and most of the time it showed you them playing it.
If you are into that kind of thing, and even if you are not, I highly recommend it as a great, quiet watch…. although, not really ‘quiet’ quiet with the way the guy sings. 
Some other really cool things which I liked about the movie were that neither of the main two actors had acted before, the guy (Glen Hansard) is from The Frames, and he wrote all the music himself… I don’t know if she (Marketa Irglova) helped. AND another randomly weird thing about the movie is that they never say anyone’s name!!!! Not once does it let you know their names….. Only I have a slight inkling that her name was Sarah. But I’m pretty sure I made that up 
Glen had a role in the Irish independent movie The Commitments in 1991. It was a small role, though, so you’re right. Neither Marketa nor Glen are professionals.
And the music for the film was written by both, so yeah, Marketa helped with that, too