It's about a boy who starts a band to impress a girl.
It's set in Dublin and London in the 1980's. 
It's directed by John Carney who made Once and Begin Again. 
It's just opened and it's getting some great reviews

'A heart-melting adolescent romance that gives teenage garage bands everywhere a better name.'  (Variety)
'Just as with Once and Begin Again, Sing Street will make you laugh, cry and leave you humming its songs for days.' (Empire)
'The most romantic movie you'll find anywhere these days, brimming over with music, fun and the thrill of first love.' (Rolling Stone)

Bono's been talking about 'Sing Street'

'I remember the 1980s with somewhat of a blush. No man's hair should be bigger than his girlfriend's.  But that was the time. Dublin in Technicolor. In reality it was monochrome and in the grip of a recession, But on video tape, you could be transported. You could wear what you liked, and the more outrageous the better. Anything to wind up the jackbooted skinheads on Dublin's north side. Make-up on a boy drove rockers wild, and the teachers wilder. 
Thank God for Bowie, who made all the black eyes okay. And allowed people to find out who they were. 
My brother gave me the gift of music through my first guitar. We formed a band.
In truth, at the same stage, U2 were not as good as the kids in Sing Street. In truth most films you'll see this year won't touch Sing Street...'