Tori Amos, Hammersmith Apollo, London<br/>Passion Pit, Concorde 2, Brighton

Amos seems visibly unhinged but, as she purrs and grabs her crotch, you can't help but be captivated

'Thank you for coming to my local and having a pint with me," Tori Amos says by way of a greeting. "It's a piano bar, and I'm gonna play for you all night." That's the conceit, at least. In reality, few Hammersmith boozers have a grand piano nowadays, still less one with green and amber neons under the lid.

She may be best known for what she does with her hands but, like a pole dancer – a profession which probably began outnumbering pianists in London's pubs quite some time ago – it's really all about the legs. Throughout any Tori Amos concert her thighs and calves, wrapped in silver Lycra and perched on killer heels, are perpetually twitching and spasming with sexual energy, just like Laura Dern in Wild At Heart when Willem Dafoe leaves the room.

It's as though she's dying for a pee on the morning commute or, shall we say, there's an itch she needs to scratch (either way, honestly, you'd think she could have got it out of her system in the dressing room before the show).

This, of course, is all part of the pantomime now. A verse or two into tonight's opener "Give", the first track on her current album Abnormally Attracted To Sin, straight after the line "some say it was pain ... or was it shame?", Amos takes one hand away from the ivories and reaches for her crotch, and the entire Apollo goes "woooh!". A few songs later, when she slips a theatrically feline purr into "Cornflake Girl", she gets an identical response. This is what Tori's paying punters have come to expect, in the same way that people used to go to Who gigs knowing it would end with Pete Townshend trashing his guitar.

You know, it's all too easy for the male concert-goer to feel disheartened and disenfranchised on the way to a show by an artist you need ovaries to fully understand. But even if you're resolutely not in the mood for shrieky menstrual music, you can't help being captivated by Tori Amos. Insanely talented and visibly unhinged, straddling a stool between no fewer than four sets of keys which she plays simultaneously, she's endlessly watchable. (Amos may have a backing band, comprising Jon Evans on guitar/bass and Matt Chamberlain on drums, but they're tucked as far into the corners as courtesy allows, without asking them to stay in their hotel rooms and play via wireless connection.)

At regular intervals, she flicks her waist-length russet locks aside and peers quizzically at us from between her two microphones, both tilted mouthwards at an angle reminiscent of gang porn, and generally shows incipient signs of becoming the mad old lady with cats in her hair from The Simpsons. When you do that stuff at 26, no one takes you seriously. When you're doing it at 46, it starts to seem all too real.

There are, of course, plenty of cause-and-effect reasons to celebrate her existence. No Tori Amos? No Joanna Newsom, no Amanda Palmer, no Regina Spektor, so come let us adore her. On the other hand, no Tori Amos? No Alanis Morissette, so let's burn the witch. Everyone has their place in the lineage, of course, and Tori Amos is the Kate Bush who actually tours (although, hearing her play "Space Dog" from 1994's Under The Pink, one could argue she's a Carole King who had one bad day too many). But is it still worth having her around? You bet your life it is.

Passion Pit's rise has been a rapid one, rocketing in a matter of months from a local buzz on the Boston scene to making waves at last year's CMJ festival and reaching the Top 10 in the BBC Sound Of 2009 poll. They are one of the surprise hits of the summer festival circuit. The appeal of the Massachusetts quintet is the Christmassy twinkle of their electronic indie-pop. Notes dangle like baubles, melody lines hang like tinsel, in a manner vaguely reminiscent of the wonderful Black Kids.

But what really grabs the attention is Passion Pit's nearly Renaissance-named leader Michael Angelakos, he of the exploded-mattress hair, who roams the stage gesticulating and testifying like a slightly fey trainee Evangelical preacher, and permanently sings in a dog-bothering falsetto so comically high that it comes as a shock between songs to hear him talking in a fairly normal, masculine voice.

It's a great gimmick, but heaven help him when he catches a cold.