It says something about Pat Collins’s typically bracing documentary that viewers – if they have not been lucky enough to catch Michael Keegan-Dolan’s Mám in the flesh – will be left yearning to see more of the ecstatically received dance piece. Collins, among the most important Irish filmmakers of his generation, begins with shots of the finished performance and then takes us back to its creation in a rehearsal space on the Dingle peninsula.

There is no spoon-feeding here. We get no helpful narration. The screen does not groan with explanatory captions. We are thrown into rehearsals and watch as the piece grows organic ally around us. Cormac Begley – who stops to give us family history – contributes swirling concertina as 12 dancers improvise abstract moves. We don't even have a developing nested narrative to cling on to. Mám, follow-up to Keegan-Dolan's Swan Lake/Loch na hEala, plays out through impressions rather than stories. Everything is process.

Yet the intricacies of development prove fascinating. “He has succeeded in capturing on film the essence and narrative of the invisible energetic process of making a new and complex piece of dance theatre,” Keegan-Dolan says of Collins.

Much of that is down to the choreographer’s unrelenting insistence on freedom of expression. He is forever telling his cast that there are no wrong answers and that any gesture will be considered valid. Eventually, through repetition and variation, the final movements emerge like sculpture from rough stone.

In truth, the sessions occasionally take on the flavour of therapy. “You support one another in the collective journey,” they are told. At least one dancer is consoled after bursting into tears. This is not (thankfully for the performers) one of those terror spaces from fictional cliche in which choreographers, long stick in hand, bellow unkindly at vulnerable ingenues. Collins’s camera, which rarely stays long with any individual character, convinces us that we are watching a family at work.

It might, perhaps, have been nice to get closer to the dancers themselves. Few personalities emerge beyond that of Keegan-Dolan. But Collins has never inclined towards the obvious. An exhilarating study of creativity in motion.

Out now in cinemas and on digital release from February 25th