For more than a decade, the International Festival has carried the torch for popular music during an Edinburgh August. But this year the Fringe looks set to have its poppermost year in some time with the advent of Big Nights, a diverse programme of live music curated by promoters 432 Presents at La Belle Angele. The line-up captures the variety and eccentricity of the Fringe, from a two-night stand with Pete Doherty to Jurassic 5/Ozomatli rapper Chali 2na, Scottish neo-trad trio Project Smok to blues singer Fantastic Negrito, plus a couple of curveballs in ‘Safety Dance’ hitmakers Men Without Hats and the 2024 Eurovision runner-up, Croatia’s Baby Lasagna.

Chief among its treasures, however, is an appearance by esteemed US outfit Mercury Rev who arrive in the city with a new line-up, fresh sound and Born Horses, their first album of original music in nine years. Singer/guitarist Jonathan Donahue and multi-instrumentalist Grasshopper are the long-serving core of the band, formed in Buffalo and now based in Kingston, New York, while Jesse Chandler and newest recruit Marion Genser add what Donahue refers to as ‘atmospheric keyboards and that cosmic microwave background.’

Donahue is partial to an allusion or two, and likens their contribution to ‘welcoming a new friend into a close circle. At first there is a new energy and then that energy settles into something that hopefully is in harmony.’ Born Horses took shape by serendipity. In striking contrast to his trademark fragile falsetto delivery, Donahue speak-sings much of the album, based on spoken-word recordings he made without a thought to musical accompaniment. ‘I wasn’t thinking I was writing lyrics, I was just passing the time,’ he recalls. ‘Later, through an accident of dragging the wrong music file, the lyrics landed on top of the piece of music I was working on, and I was quite surprised at the impression it left on me. I followed it like following a bird through a forest for a moment.’

Gradually, over a number of years, the band finessed a ravishing and surprising ambient backdrop for Donahue’s poetic ruminations, featuring long spacious takes of noir-ish trumpet, sonorous organ, plangent piano, and soft, shimmering percussion. It moves the band into somewhat jazzier territory than the chamber indie sound of old, and from more conventional songwriting territory into meticulous composition. Donahue is happy to acknowledge the influence of trumpet maestros Miles Davis and Don Cherry, and experimental composers Pauline Oliveros and Terry Riley, but stresses ‘we’re not jazz or blues musicians; we’re not classical. We are probably very punk at heart. To us, rock’n’roll didn’t stop at Chuck Berry, punk rock didn’t stop and start at the Ramones, and jazz doesn’t start in the 1960s. So all of these elements are close to our hearts.’

There is a quiet radicalism at play in Born Horses which marks a new chapter in Mercury Rev’s slow-burn story. ‘As we get older, patience is a member of the band; it might even be the bandleader,’ reckons Donahue. ‘You’re like a bat sending out this sonar. You’re waiting for this ping to come back to you. You notice you are probably on the right track when you start to feel that uncertainty deep inside, that uneasy feeling of “is this going to be career suicide?” But it’s that uncertainty that gets you out of bed later in life.’

Mercury Rev, La Belle Angele, Friday 29 August.