What Midsommar is based on: a real Swedish village, a real devil-fiddler legend — and Ari Aster's own breakup

Midsommar's great trick is making you suspect that all of it — the runes, the cliff, the bear — might be documentary. It isn't, quite. But three genuinely real things hold the film up, and they're stranger than most of what Ari Aster invented.

Hårga, where the Devil brought a fiddle

The commune in the film is called the Hårga, and Hårga is a real place in Hälsingland, northern Sweden — a village with a proper Satanic CV. Swedish folklore, preserved in the song "Hårgalåten," holds that the Devil once turned up there disguised as a fiddler and played so irresistibly that the young people danced themselves to death on Hårga mountain; mid-song, the doomed dancers clock the hoof where a foot should be. Cheerful stuff.

That legend is alive and well. Locals re-enact it every year — an elder narrates, everyone dances, and the last woman standing is crowned queen — which is more or less shot-for-shot the competition that makes Florence Pugh's Dani the May Queen. There's even an annual dance, the Hälsingehambon, that sets off from the Hårga meadow. Aster has said the legend was one of the starting points for choosing the setting; the film's Hårga is otherwise his own, built from scratch in Hungary.

The rest of the research pile

Aster and production designer Henrik Svensson travelled through Hälsingland before writing a frame, and it shows:

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• The painted farmhouses. Hälsingland's centuries-old murals inspired the commune's wall art — imagery Svensson described as unsettling in "a biblical, scary way," and easy to nudge towards the horrific.
• The runes. The Hårga's alphabet was built with academic advisers on the real runic system; the blood eagle comes from Viking myth.
• The Swedes started it. The film exists because producers Patrik Andersson and Martin Karlqvist pitched Aster a Swedish folk-horror after Hereditary — hence the end-credit oddity "Concept of the Hargas by."
• The rest is invention — the fruit-stuffed corpse included. Aster, asked how much is real, put it at hundreds of sources: "there are hundreds of things kind of woven together here."

And the third true thing: the emotional engine. Aster sat down to write shortly after a tumultuous breakup of his own, and rebuilt the producers' folk-horror pitch around a disintegrating couple — which is why the scariest scene in the film is arguably Christian forgetting Dani's birthday. As for his approach to the ritual sex scene, Aster's own summary is hard to better:

"I tend to ruin sex for people."

The real Hårga, for the record, still holds its dance every summer. Attendance is voluntary, and everyone goes home.

Earlier we wrote: American Horror Story 13 review: Jessica Lange is back for a greatest-hits season