The ten-strong cast of Acaprov have some difficulty fitting both their numbers and their enthusiasm on a four foot square stage. But they don’t let the space restrictions impede them in constructing a new, improvised, a capella musical for every show.

The show I saw was spawned from a location prompt (a library) and a suggested title (“Check it Out!”) shouted out from the audience. Then commenced the epic tale of Laura’s first day working at the library, when Evil Aisle 13 tries to take over. Laura and Library Manager Susan must use the combined powers of confidence and friendship to defeat the mansplaining, while also distracting the inspector who is threatening to close the library altogether.

There is no preparation time or opportunity for consultation, as the whole cast are on stage throughout. Some provide the beat and backing vocals while others take on speaking roles to present the story. They have no props and no set, but still managed to evoke different areas of the library through physical movement and dialogue. They also make it more difficult for each other in amusing ways by pushing scenes in certain directions or asking cast members to make up or repeat specific things.

It’s a bit ragged in places, with the cast sometimes missing cues or more than one trying to take control at any one time. But the members of Acaprov totally own the occasional awkwardness of improv gone wrong, which just makes it all the funnier. It’s a family show but they include both topical and more intellectual jokes for the adults. The plot isn’t always coherent and the structure of the songs is very simplistic, but I was still singing one of the main refrains in my head on my way out of the venue, and that’s always a sign of a good musical.

Overall, the cast of Acaprov make up in enthusiasm what they lack in polish. Their self-deprecating humour and ability to roll with whatever their fellow performers throw at them allow them to fold any mistakes or problems into the show. And that’s what improv is all about.