Lucky Soul, The Lexington, LondonAmazing Baby, Proud Galleries, London

So long, Marianne: Ali and her gang reach out to the pure-pop faithful

Pure pop is a faith, and Lucky Soul are a band for believers. More than that, in fact: they're a band of believers.

The Great Unwanted, the 2007 debut album by the Sixties-inflected sextet, was a romantic and heartfelt treasure, adored by all who heard it, or at least everyone in possession of the full complement of aortas and ventricles. "An immediate classic" was my judgement at the time, and I'm standing by that. And, on the evidence of this comeback concert, in which they showcase material from the forthcoming follow-up (due early 2010), they've got another one up their sleeves. A band member tells me it'll be "darker" than its predecessor, but I've got my fingers crossed that's just the sort of thing musicians feel they ought to say when they're coming off the back of something ultra-sunshiny, and that however dark it gets, somebody remembers to leave a light on.

Lucky Soul don't stand alone: they share a stable with popped-in, souled-out co-religionists. I've always loved record labels that have a distinct aesthetic, and Ruffa Lane, which is co-run by one band member and one ex-member, is such a label. It's no coincidence that Napoleon, the 10-strong Dexys-meets-Springsteen crazies from Uppsala, are Ruffa Lane signings, as is tonight's support act Montt Mardié, a bespectacled bear of a man from Stockholm who only writes songs about his girlfriend Annie, all of them ebullient to bursting point. When he bashfully announces "I love you, Annie!" before his last song, the whole place goes "Awww". He's thoroughly disarming, which is especially welcome in a city where everyone's armed.

We've already had a taster of Lucky Soul's second album in the stunning shape of "Woah Billy", quite simply one of the under-the-radar singles of 2009. A bewitching brew of T Rex, Dusty and Blondie, with a poignant pinch of self-doubt (in the literalist way that only a song with the refrain "I've got some doubts about myself" can be), it's a step forward from the contained Ready Steady Go! stylings of The Great Unwanted. Seriously, log on to your computer and do whatever it takes to hear it: it's one of those songs that forces you to go back to the start and listen again the first time you play it, and once you've done that, it's inside your head and inside your world all day long.

The Greenwich group, led by the core couple of Andrew Laidlaw and Ali Howard (who, with her honey-blonde hair and high-necked Sixties dress, is the spitting image of Marianne Faithfull circa "As Tears Go By" tonight), kick off with "Woah Billy" at the risk of shooting their load early, which takes some nerve. As, in Ali's case, does being here at all: "I've just come out of hospital," she says while kicking off her shoes, Sandie Shaw-like, "and I'm a bit wobbly. How about that, Liam?"

It's the self-confidence of a band who know they've got an immaculate collection of material to draw upon, from The Great Unwanted's title track, with its knowing Lesley Gore quote, through possible future singles "Ain't Nothing Like a Shame (To Bring It All Back Home)" and "White Russian Doll" with its driving Vandellas beat, to "Get Out of Town", featuring a cameo from Brighton girl group The Pipettes on backing vocals. And, indeed, the self-confidence of a band who can afford to leave out their finest moment, "Add Your Light to Mine", completely. Needless to say, I'm (still) a believer.

You can't have failed to notice that something is happening in New York. Something floral and lysergic and smelling of incense and peppermints. The preppy uptightness of the post-Strokes scene is all but over (with Vampire Weekend its Afrobeat-dabbling last hurrah), and a new spaced-out hippyism is in vogue, from MGMT to Yeasayer and beyond. It's as though some slow-travelling psych-wave has taken four decades to roll eastwards from Haight-Ashbury and has finally broken in Williamsburg.

Amazing Baby are too much. Like MGMT themselves (who are tellingly prominent among their top MySpace friends), they write songs in which one tune is never enough, and in which multi-melodies overload the senses. It's a tribute to their power that at this warm-up for the Reading Festival, attended by celeb scenesters from the great to the gormless (that's Beth Ditto to Peaches Geldof) with paparazzi flashbulbs popping all around, it's possible to completely switch off your surroundings and lose yourself.

The Brooklyn band, torsos creased in half, hair threshing, are blatantly oblivious to the celeb-splattered context too, which helps matters. And with songs like the irresistible martial march of "Bayonets", the concussed prog-glam daze of "Pump Yr Brakes", and "Head Dress", which sounds like three copies of Bowie's "The Bewlay Brothers" playing at the same time, slightly out of sync (which is actually way cooler than it might look on paper, you'll have to trust me on that).

Slowly but surely, one central fact emerges clearly about Amazing Baby. There's an invisible comma in the middle of their name.