Two songs into his SummerSalt festival set at Thomas Dalton Park, it's just Harper up there - no band for this Australian visit, no vocals even, for this song.

The heaving, hyper crowd that accompanied his recent collaborative stint with pop megastar Harry Styles is nowhere to be seen.

Harper sits bent over the lap steel slide, making his magic, somehow holding this big, diverse festival crowd fascinated - and he'll keep them that way for 14 songs.

The blues slide ace might have almost hypnotised himself at one point, seeming to come to at the end of the instrumental.

"Hey. Hey! How you doing?," he says, before accepting a flower crown from the crowd with trademark, infinite courtesy - "If you don't mind I'll save it possibly for my daughter ..."

Harper dials the vocals up to Aretha Franklin-esque heights for a verse of Diamonds on the Inside and delves deep into the blues for I Trust You to Dig my Grave.

Burn one Down is as eloquent a case as ever for legalising marijuana. Written almost 28 years ago, the lyrics find a free and easy home between the humidity-hazed escarpment and the sea - "if I'm causing no harm it shouldn't bother you".

Harry Styles' Boyfriends - poignant already in the hands of the 28-year-old Briton - becomes an event highlight and a knowing lament in Harper's voice of warm butter and life experience.

A rootsy cover of Springsteen's Dancing in the Dark prompts a singalong. Another cover - When the Levee Breaks (by Memphis Minnie and popularised by Led Zeppelin) - causes many to pull out their camera phones.

Harper and City and Colour, AKA Dallas Green, mark SummerSalt's first foray into international acts, with Wollongong the second stop in this year's eight-venue Australian tour.

Set metres from the beach, a welcome northeaster flushes out the worst of the day's heavy heat. With scant nearby parking but the train station an easy 10 minute walk away, the festival has found a smart home on the eastern edge of Thomas Dalton Park.

The best - certainly the cheapest - seats may go to a few outside the festival fence, perched on the sand or in the trees that stabilise the dunes at Fairy Meadow.

Many arrive early despite that soupy heat, testament maybe to the pulling power of festival opener Alex the Astronaut.

Skydivers fall to earth in the distance as Middle Kids's Edge of Town gets the crowd moving.

More than one music fan has arrived with a baby strapped to them, or a toddler in noise-muffling headphones. A baby crawls contentedly along a line of yellow flooring that conceals the show's sound cables.

The Wollongong crowd has made itself at home with oversized gaps between rows of bring-your-own-camping-chair seating and plenty of beach carts laden with water bottles and family-sizes packets of Doritos.

Save for a stray expletive or two from the stage, the festival makes good on its family-friendly pledge, with face-painting on offer and miles of green lawn, though at $102 for kids aged over two, ticket prices will give some parents pause when it comes to booking next year.

The Rubens pull a crowd of 20-somethings to their feet at the front of the general admission area; City and Colour is all languid cowboy guitars as the sun inches closer to the escarpment.

It pays to have arrived early, with no big screens to let those at the back know that Harper's t-shirt says 'Rosa Parks' or that the trumpet up front is coming from Julia Stone's lips.

Private Lawns, complete with an extended banjo instrumental by noted session musician Ben Edgar, is an early highlight for headliners Angus and Julia Stone, and - drawing hoots at least one hat skyward - seems to shift the festival up a gear.

The Stones' musical chops are on full display, with Julia's trumpet featuring in a cover of Streets of Your Town and Angus hitting the harmonica for an old song about a long-ago drive "from Sydney to these parts", Wherever You Area.

Fluffy white clouds bloom on the screen behind Angus for Big Jet Plane.

Two of Angus' Dope Lemon numbers - Home Soon and Uptown Folks - produce the event's liveliest moments, the latter a night highlight.

It's ten minutes til closing and Angus, the less talkative of the Stone siblings, is a suddenly commanding presence, one of three big guitars rattling any notion of sleepy summer festival.

Chateau and a pared-back Santa Monica Dream encore bring the crowd back to earth, and keep the neighbours happy, as many pack up their chairs and shuffle to their feet.

Under pinks lights, guitars in hand, brother and sister end the night with a hug.