One learns the strangest things at festivals. That, for instance, this summer has been a bit of a blackcurrant disaster in the UK because the extreme heat caused all the different varieties to ripen at the same time and fall from the bushes before they could be properly harvested. That fact came from a retired Kentish farmer called Ian, next to whom we were sitting at a £65-a-head dinner at this year’s Green Man, just outside Crickhowell in Wales.

That alone should spell the difference between Green Man and the scene depicted in the Netflix series Trainwreck: Woodstock ’99. No one here was getting mouth ulcers because the drinking water was running with sewage, or rioting, or burning the catering tents down (what a waste of slow-cooked Welsh lamb that would have been). And, naturally, there was nothing on the stages resembling nu-metal, the misbegotten hybrid of rap and metal that riled up the Woodstock masses, to mobilise any seething resentments about fractionally overdone falafel from the stalls.

One of the delights of festivals is catching up with acts you’d decided were one thing, only to discover they’re actually something else entirely. Take Penelope Isles, whom I had pegged as pleasant and slightly wispy indie-poppers (and, having just gone back to their recordings, I discovered that assessment was not entirely wrong). Their set on Thursday evening started that way, but then built and built until the last ten minutes were throbbingly intense, and not at all wispy.

See also Beach House, the Saturday night main-stage headliners, which seemed to me like a colossally misguided booking until they actually began. The US trio, permanently backlit so that their faces remained invisible, were a quiet storm of impassive grandeur, huge synth washes and pinpoint guitar arpeggios. Through a big PA system, it was like being instructed to cower before your new alien overlords. If it was all a bit one-note – there’s only so much you can do with dreamy guitars and overpowering synths, topped by affectless vocals – it was a perfect note to strike in the setting.

The best thing I saw all weekend, though, was Jessie Buckley and Bernard Butler. She’s so talented – terrific actress and singer and charming too – it almost feels unfair. And he has stealthily become one of music’s best enablers, as producer and collaborator extraordinaire. If you haven’t been paying attention, you might still think of him as That Bloke Who Used To Be In Suede, but that’s a long time past. He now covers not just the waterfront, but pretty much the entire musical shoreline, working with anyone who takes his fancy. Sometimes that means big hit singers, sometimes it means tiny indie bands, but it usually signals something pretty interesting.

He and Buckley make a kind of filigreed folk-rock, owing a fair amount to Pentangle and the like – maybe a bit of Tim Buckley at his most direct. Butler, who can play the socks off pretty much any other guitarist, kept everything in the service of Buckley’s remarkable singing.

The band was simple – as well as the principal pair, there was just a drummer and an upright bassist (furthering those folk-rock links; Danny Thompson was a crucial part of the Pentangle sound, and the bassist on Buckley’s great Dream Letter live album). It meant everything sounded uncluttered and precise. On a warm summer evening in the shadow of the Brecon Beacons, it was hard to imagine anything lovelier.

A shout out, too, to a couple of bands wholly unknown to me – Preen, who make the kind of lush, post-Beatles pop that always goes down a treat (listen to Emitt Rhodes on Spotify and you’ll recognise the sound I mean: big on piano and bouncy melodies); and Papur Wal, singing in Welsh, making the kind of lazily fuzzy indie rock that hits a bunch of my sweet spots.

It was a new band that made me leave Green Man on Sunday lunchtime. I wanted to get back to London to see the teenaged female quintet House of Women, who are so new as to be almost completely unknown – just a couple of tracks on YouTube – but excitingly promising.

None of the individual elements of their music break new ground – a bit of grunge, a bit of stoner rock, sometimes a bit punky, sometimes a bit metal – but the way they combine them is interesting and fun (and the drummer’s fills have some of the eccentricity of Keith Moon).

Their singer, Kyla De Boer, is fantastic – a voice pure and almost folky in the quiet passages, but then roaringly strong, yet without resorting to clichéd rock phrasing. They’ve got two very good songs, but nothing in their short set was bad, which is a miracle for a young group. Predictions are pointless but I’m excited to see where they might go because there’s a real spark there.