When America first sold us the pop dream, half a century ago, it never warned us about this part: the spectacle of the visibly very mortal authors of immortal songs, singing those same old tunes with the added poignancy of age. When Brian Wilson, a cuddly old silver fox in a rugby shirt, asks "Wouldn't it be nice if we were older?" we know he knows the answer all too well.

The gently-coaxed comeback of Brian Wilson has been one of the musical miracles of the modern age, for this is a man who, as a mixture of myth and reality would have it, lost it so badly that he spent a decade living in an indoor sandpit, defecating and growing his beard. His superb band is still led by familiar faces: the one that looks like Robert Redford, the one that looks like Jerry Hall, the one that looks like the guy from Eraserhead, and the one did look like Jeff from Curb Your Enthusiasm but has slimmed down. With their help, sitting behind an autocue and a mostly untouched keyboard, he's found a comfort zone without the need for sand, and the confidence to let that yearning voice fly free.

An educated crowd, then, indulge Wilson's eccentricities (acting out every word of "Sloop John B" with kindergarten hand movements, for example) without too many giggles. Respect, after all, is due to the man responsible for the vertiginous vulnerability of "God Only Knows", introduced as "Paul McCartney's favourite song". Wilson repays the compliment by ending the night with McCartney's "She's Leaving Home". There was a time, of course, when the Beach Boys and the Beatles were racing neck-and-neck to outdo one another, wrestling with the possibilities of what pop music could be. To my mind, Wilson won, and his friend and rival never wrote anything to match "Heroes and Villains" (we get the full-length Smile version tonight).

The second act of Wilson's show is a new work entitled That Lucky Old Sun (a Narrative), which cannot help but sound like a Beach Boys act with lines such as "forever she'll be my surfer girl", or the rhyming of "ocean" with "notion".

"We'll break the silence in just a couple of minutes ..." he says, calming the crowd's impatience during an intermission. He pauses, then wisecracks: "It was all silence before we came along." It's an exaggeration, but after a shamelessly feelgood encore ("Barbara-Ann", "Help Me Rhonda", "Surfin' USA"), he has a point.

From the sublime to ... well, to Paramore. Or "Para-fuckin'-mooore!", as their singer Hayley Williams unconvincingly puts it. They may perform in front of the word "Riot!" and a mural of civil unrest, but "Onward, Christian Soldiers" would be a more honest slogan for these Tennessee teens. They are, you see, Bible-bashers, with songs about striving for salvation through the Lord.

Even if you didn't know this, you could guess. Paramore – Williams backed by three guys in matching red jeans – are a Disney's High School Musical version of emo: imagine McFly with a punked-up Olsen twin on vocals. Their cliched dynamics raise high-pitched screams from 2,000 kids cutting loose after their first week back at school, but it's all a bit Kelly Clarkson. When the shrill, squeaky-clean singer throws the least sincere devil sign in rock'*'roll history, and the Paramore fans throw devil signs back, you can bet she prays for forgiveness the next morning.