The Modern Maori Quartet's theatre offering is a little flimsy as a cohesive performance: there is a slim narrative of four souls in the antechamber of the afterlife, awaiting the move to heaven and trying to discover what is holding them back. While this gestures towards a comment on the past century's treatment of Maori culture, the concept comes across as a gimmick to frame the individual songs and monologues. Each member of the quartet comes from a different era – a war veteran, a nearly-was musician, a hip man about town and a contemporary student – and together they trace a social history of Maori masculinity. Each one gets the routine that reveals their unspoken truth, forcing them to confront their demons. Within this structure, the Quartet rock and swing through a series of entertaining and heart-felt numbers that combine their beautiful harmonies and lively musicianship.

The most telling story is 'uncle': his rejection of Maori language reflects his own negative experience at school, leading him to a lifelong struggle. The surface veneer of a smooth ladies man who liked a drink is stripped away to interrogate the treatment of Maori culture within the educational system, and the show's message of self-love is firmly connected to a wider acceptance and celebration of heritage. Bub, the youngest character, however, gets the best song-monologue: the quartet drop into a brutal haka that captures the pressures of modern life in its warlike gestures, stomps and chants. Simultaneously a reworking of indigenous dance and a thrilling commentary on psychological anguish, it is stunning and injects a moment of terror into the slick production.

An example of how cabaret can be developed into an extended narrative – a genre that member Rutene Spooner works to more autobiographical effect in his show Super Hugh-Man – Two Worlds has charm and warmth, cheek and humour, and superb musicality that contains fragments of brilliance and intensity.

Assembly George Square Studios, until 26 Aug, 3.50pm, £12 (£10).