The Waterboys @ Ross Bandstand, Edinburgh 28 August

You can’t look away from Paul Brown. The Memphis keyboardist and relatively new Waterboy wears a wildman’s grin through the entire show and plays eagle-armed, low over his Yamaha Motif XF7, breaking his manic gaze only to whip his blonde locks hard enough to put Willow Smith to shame. His enthusiasm is palpable during Nearest Thing To Hip, a new song off Modern Blues, dedicated to “the Old Edinburgh, the parts that are no longer with us.”

Brown never knew the cafes and music shops Edinburgh native Mike Scott used to frequent, but he helps turn the record’s bittersweet eulogy into a searing expression of loss and joy in what was. He seems to be experiencing severe electric shocks, or else attempting to ward off a badger’s love caresses beneath his keys while finishing the solo. No matter what exactly transpires onstage, the solo is thrilling, in a style combining stride, P-Funk, a bit of John Paul Jones, a bit of The Blues Brothers and James Brown’s The Old Landmark – but 100% rock and roll.

It’s a peak, but not the highest point in a night that just keeps getting better. The show starts with a short set of “nice soft folk music” from Freddie Stevenson, accompanying The Waterboys on this European tour. It’s good stuff, folk with some dark and surprising chord changes, Stevenson and Waterboys collaborator Joe Chester occasionally harmonising in the style of Simon and Garfunkel or The Milk Carton Kids – though something in Stevenson’s voice suggests he’s served his time as a howler, too. Not for the last time that night, the sounds and the scenery dovetail on Until The Devil Gets Payed, when certain clouds part to illuminate the castle in Edinburgh’s late summer 8pm gold.

By the time the Waterboys take the stage a thick crowd huddles for warmth, stretching almost back to the railings of Princes Street, where about two dozen at any time stand gripping the bars and watching Scott and the latest Waterboys: veteran fiddler Steve Wickham, Texas geet-player Zach Ernst, David Hood on bass, the Professor Ralph Salmins at the kit, Brown on keys. We’re not all aware of it, but this is an assemblage of some of the world’s most accomplished session and touring musicians – their collected CVs might be thicker than the Fife phonebook.

And though they’re not one of those uniformed and choreographed touring acts – Brown’s orgasmic spasms are a sharp contrast with Hood, at the opposite end of the stage, who in a blue button up and modest gray suit seems to sit in that state of chronic geriatric confusion we associate with Harrison Ford – but they blend more like a sextet with thirty years practice than six veterans of varying tenure thrown together for a tour: Scott and Wickham kick and twirl together; the youngest, Ernst, knows when to shred and when to bend and when to blend with his elders; and the fiddle and keys weave so well they’re as hard to separate, sonically, as waves from the ocean. And it’s incredible that three grown men twirling three times in unison, on Fisherman’s Blues, can bring so much joy to a crowd. The performance, the sound, the mix of old songs and new songs and anecdotes is all so fluid, down to the subtle shifts in Wickham’s playing from elegant baroque to reeling Scots-Irish folk to forge-hot rock and roll: we might ask how we can know the dancers from the dance.

Or maybe that’s just Willy B’s influence, which first pops up during a moving rendition of The Song of Wandering Aengus, signaling Scott will perform some material from An Appointment With Mr. Yeats. When Scott recalls catching the 12 or 27 bus at Princes Street and looking down into the gardens, wondering what it would be like to play the Ross Bandstand, he probably didn’t see himself longhaired and mantis-armed wearing a white three-faced mask and chanting eschatological poetry. But he does exactly this, following a sort of pageant in which Brown and Wickham, in black beaked masks, clash in a fiddle-organ battle of shrieking effects, trading bars and each reeling as the other attacks. Scott struggles larvatus to the mic; he grips it, and recites Yeats’ Second Coming, with keys and fiddle diving and screeling behind him.

This may in fact be the high point of the night but we’re still delighted when the first Roman Candle bursts above the lit castle’s Argyle Battery, seconds after the Waterboys leave the stage. With such a back catalogue of hits most of us know, it would be impossible for the band to satisfy our every wish (some chanting the obscure Sympathy For David Icke leave just a bit disappointed). Still, they might come back and play, oh, Bang On The Ear, for old time’s sake?

Not tonight. Instead Wickham and Brown segue an excellent duet into a hard rocking signalong cover of Prince’s Purple Rain (perhaps recalling that artist’s 1993 Meadowbank concert, one of the best shows the city’s seen, some say). After two false endings and uncountable choruses, they close with a classic, The Whole Of The Moon, just as the near-full moon looms up, cloud-shrouded, ‘tween the Hub and New College’s twin peaks and more pyrotechnics burst above us; we all sing together, even Brown, who ditches the keys and throws his arms wide like a man ready for a midlife career change in one desperate off-Broadway audition. Plenty of us do the same, wearing copies of his loony, contagious grin. The Waterboys take a final breathless bow and we stream out of the gardens, walking in a mass trance through faintly fragrant roses and under the pop and sigh of brilliant fireworks.