Not all that far from Buxton, on what's now the outskirts of Manchester, stands Prestwich Hospital – built in the Victorian age, and once Europe's largest asylum. In the fittingly-period setting of the refurbished Pump Rooms, Buxton Drama League recreates this most misunderstood of institutions, introducing us to both its patients and the staff charged with treating them. Eric Northey's 2011 script bears the hallmark of careful research, and – as the powerful ending makes clear – it's based on real-life tales from the asylum's records, all drawn from a relatively short period 100 years ago.

Those stories are more nuanced than you might be expecting. Yes, we see evidence of ignorance and casual misogyny: a single mother separated from her baby, a troubled patient who's shouted at like a child. But the overall message is that our forebears did their best, within the constraints of their knowledge and the attitudes of their time. Dr Perceval, the sometimes-misguided psychiatrist whose story forms the backbone of the script, is fundamentally well-meaning – even when we discover, late in the play, exactly what his obsession with "measurement" actually means.

The large cast has no weak links; this is technically community theatre, but the standard is easily at the level of a professional company. Stand-out performers include Corinne Coward as the religiously-obsessive Ann, whose extended, half-crazed outburst is just comprehensible enough to hint at childhood forces which made her that way. Dave Carlisle has a powerful monologue too, perfectly synchronised with an impressive First-World-War soundtrack, and Dan Large reveals Dr Perceval's emotional heart as the hopelessness of his situation begins to overwhelm him.

Northey's script is filled with grim humour, and – perhaps more surprisingly – it's also punctuated by songs. Some are performed as ensemble dance pieces; others explain individual characters' back-stories. A few of the songs are intentionally grotesque, making creative use of the unusual setting to capture a cartoonish sense of confinement and horror.

But while these individual components are effective, the combination is a curious one. The programme notes reference Brecht, who famously argued that theatre should "make the familiar strange" – and the incongruous music-hall turns certainly tick the "strange" box. But there's nothing remotely Brechtian about the remainder of the scenes, which are presented in a creative but thoroughly conventional style. The contrast was a little too much for me, the transitions into and out of the songs more perplexing than discomfiting.

In the end though, this is an uncomfortable story; not so much because of what it says about the past, but because of the light it shines on modern society. Ironically, it's the Victorian-era superintendent – who we see retiring at the very start of the play – who seems to show the most sympathy and understanding. He can't treat everyone who comes through his doors, but they're "warm and well-fed" in his care. A hundred years on, can we honestly say the same?