As conjured by a score of original Irish-inflected songs, written by the original stars of the film Glen Hansard and Markéta Irglová, the atmosphere is partly a busked concert and partly an aching romance that feels both spontaneous and freshly minted. The music, played live by the actors themselves, is alternately beautiful and rousing, and Enda Walsh's script quietly overwhelms with its sense of spirit, sincerity and solitude.
There's no other show quite like it. It's the most unusual, unique and affecting musical you're ever likely to see. It has a spontaneous free-form improvisatory vitality, yet it is also emotionally precise in the understated air of longing that anyone who has ever been in love will recognise instantly. And audiences will fall head over heels in love with the show, too. Once is a genuine one-off which you'll need to see at least once -- but it's also unlikely to be your last time, as you'll want to see it again (and again).