Joanna Newsom, ICA, London

Ridiculous, then sublime

The San Francisco-based nu-folkstress Joanna Newsom may count Neil Young and Will Oldham among her fans, but you could be forgiven for thinking that they are ignoring a major elephant in the room: Newsom sings like a four-year-old witch. With her scratchy squawk, not unlike the noise a cat makes when there are fireworks outside, delivering words that sound as though they were chosen for their cuteness from some old-fashioned rhyming dictionary, she risks appearing irredeemably pretentious.

The twee folksiness remains irritating even when you get to like her. A willowy blonde, her first actions on stage tonight are to coyly bite her lip and then her tongue before belting out an a cappella number as the audience clap. This is homespun, brown-bread-ice-cream folk, coupled with the same put-on kookiness that puts people off the likes of Björk and Tori Amos. She even says "thankee", for heaven's sake.

But somehow, the quality of Newsom's work majestically drowns out all of these bad-taste alarm bells. She plays her unorthodox voice like a rare and difficult instrument - as if accompanying herself on the harp were not challenge enough. What appears comical upon first listening soon reveals itself to be highly communicative. She delivers her words stridently, savouring every syllable and hammering home the melodies. The singing style and wordiness combine to create something better than either - from the ridiculous to the sublime, so to speak.

Her melodies, influenced by traditional Appalachian folk - "This is not my tune, but it's mine to use," she declares on "Sadie" - are pretty and varied. The "na, na, na" chorus of "Peach, Plum, Pear" segues into a riff played on the harp as though voice and instrument were one and the same thing. The song is played on a harpsichord on Newsom's album The Milk-Eyed Mender, so the harp version is a surprise highlight. Its sweet tale of nervous romance proves there is real substance to her sometimes cloyingly symbolistic lyrics.

Still, an evening consisting entirely of obscure little songs about love, fruit and strange creatures might have come across as tiresomely self-indulgent in the current climate. A lot of new American folk seems to be snobbishly aloof from political engagement. Not Newsom, it transpires. Halfway though the set, she announces a new song "about some of the horrible things that are happening" to the US.

"What we have known", the B-side of her single "The Sprout and the Bean", is an epic lament for America's lost values and the "miniature agonies that travel westward on the breeze". Her fingers trip across the harp strings in a beautiful musical translation of malaise. And she doesn't sound remotely like a child when roused almost to anger singing about "all the baby boys we've borne" being sent off to die. It is easily her best song: heart-rending and haunting, but too complicated to be trite or manipulative. This is what folk music in 2004 should sound like.