A String Section (Summerhall)

Five women. Five chairs. Five saws. That's pretty much the sum of Reckless Sleepers' happening, but what a manifold and meaningful piece it proves – without doubt, one of the most gripping and visceral things I have seen this festival.

Onstage five wooden chairs sit in a line, each a different shape and style, but all domestic and old-fashioned. Five women in slinky black dresses – the sort that professional musicians wear to work – walk on and stand facing us, handsaws hanging from their left hands. They stare at us, then sit, and eventually, they start sawing.

The saws become bows and the chairs stand in for cellos. This is a symphony of sorts: a harsh, hoarse burr, sometimes high and fast, sometimes low and slow. Occasionally their sawing finds a harmony, but more often it clashes. How, you wonder, is this music? Are they playing together?

It's an awkward action, sawing. Each bends down double or lies flat on the seat, straining to get a good angle of approach. Their bodies make shapes: legs akimbo, bums in the air. They wrap themselves round the wooden frames. When the bottom of a leg pops off, the chair tips its balance and soon enough, the uniformity is all askew. Chairs tilt this way and that. The women do too. The image is absurd, but, at the same time, desperately sad.

'As harrowing as it is beautiful'

Five women concertedly undermining themselves for no reason whatsoever. It's so self-defeating, so futile, so stupid. When they pause and stare blankly out, they look almost confused, as if asking why they're doing this and, more to the point, why we're watching.

It's hard work, as well, the sawing: muscular and precarious. Every so often, a blade slips out of its grove. You picture steel slicing through bare leg or someone goring themselves on a wooden stake, and you can't help but wince and flinch. You think of manual labour but also, inevitably, of sex work. These are sexualised bodies, often on their backs, and the sawing action is – ahem – familiar. Art, too: performance is a form of labour as well.

The more the piece goes on, the more it grows. Ideas layer up and images get stronger. Chairs become wonkier and body shapes, bolder. Arms get tired and sawing gets harder. So does watching. It's a dense, restless, slippery thing; as harrowing as it is beautiful.

A String Section runs at Summerhall until 27 August