Music is a lifeline for Abigail and Shaun Bengson. Baring their souls through song, Ohio is introduced as a “death concert” in response to the indie-folk musicians’ young son asking what happens when we die. But this bittersweet story of family, faith and loss is almost ferociously about grabbing hold of life.

The Bengsons create harmonies that glide directly to the top of your spine. Both clearly feel the music in their bones, but it’s Abigail who shows it, her body unable to resist moving to the tumbling scales they create together, her bright, beaming face turned up to the sky. Director Caitlin Sullivan helps the pair gracefully shape their story on stage, treading softly between gig, presentation and choir rehearsal.

The potted narrative sticks closer to Shaun, who is the drily comic balance to Abigail’s bounding enthusiasm. Guiding us through his repressive Lutheran upbringing, he eases out of the religion’s grasp but holds on to what faith means for his father, and what his father means to him. Narrowing our focus, the show homes in on Shaun’s degenerative hearing loss. In one revelatory scene, their microphones are modulated for us to understand what Shaun hears now, certain tones and consonants absent to him, then thickening and distorting as that blank mugginess will intensify over time. With creative captions that tremble as the sensory experience distorts, this slow theft is devastatingly wrought.

The pair create the atmosphere of holding our hands throughout, with angelic, ululating folk song accompanying the thoughtful ways they see and explain life. Their story serves as both a formal introduction to them as a couple as well as a deeply spiritual meditation on the world we live in. A revenant hush accompanies everything they say. A song to Shaun’s choirmistress who helped a shy, almost unspoken child unfurl is shattering. Made freshly aware of time slipping through our fingers, no one wants to miss a moment.

• At Upstairs at Assembly Roxy, Edinburgh, until 24 August. Then at Young Vic, London, 30 September-24 October

• All our Edinburgh festival reviews