'Kneecap', the name of the Irish hip-hop group and the music biopic about – and with – the groundbreaking trio, premieres today in more than 700 cinemas. It is the sequel to an American tour last fall and the precursor to a new tour.

The hybrid documentary, which was a high-profile Sundance title when it was scooped by Sony Pictures Classics, recently screened extensively at the Galway Film Fleadh and was named Ireland's Oscar International Feature entry.

It is written and directed by Rich Peppiatt and stars band members: Naoise Ó Cairealláin “Móglaí Bap”; Liam Óg Ó Hannaidh “Mo Chara”; and JJ Ó Dochartaigh “Dj Provaí” as themselves, but it is a script, and actors including Michael Fassbender play their younger selves and family members. With Josie Walker, Fionnuala Flaherty, Jessica Reynolds, Adam Best and Simone Kirby.

The film follows Belfast schoolteacher JJ into the orbit of self-proclaimed “low-life scum” Naoise and Liam Og. When the three come together, the needle drops on a hip-hop act like no other. Rapping in their native Irish, Kneecap quickly become unlikely figureheads for a civil rights movement to save their native tongue. Having to overcome the police, paramilitaries and politicians who tried to silence their defiant voice, the trio’s anarchic approach to life often makes them their own worst enemies as they create a global rallying cry for the defense of indigenous cultures.