Joanna Newsom, Royal Festival Hall, London

"I found a little plot of land/ in the garden of Eden," opens Joanna Newsom. Sitting at her wooden harp, slender in a diaphanous pink-and-white flowing dress, her hair cascading down her back, she does seem rather celestial, her angelic voice cooing, "I believe in innocence."

Angelic is not how that voice has always been described. When Newsom released her startling 2004 debut, The Milk Eyed Mender, her vocal style was variously compared to a child, a witch, a creaking door. Her idiosyncratic delivery of abstract, poetic lyrics (lines like "catenaries and dirigibles" had listeners reaching for the dictionary), while not to everyone's taste, won her an army of obsessive fans. Her second album, Ys, was a hugely ambitious record with a full orchestra, that confirmed Newsom as a major talent.

Then, last year, she developed vocal-cord nodes which had to be removed; when her voice returned it had lost its high-pitched rawness. The Newsom of 2010 is decidedly sweeter, most obviously so on the few tracks from her first album. The piano waltz "Inflammatory Writ", accompanied by banjo, now has a music-box tinkling quality. "The Book of Right-On" reveals most clearly the changes: some notes seem a stretch, and its multi-instrumental arrangement sounds rather cluttered.

While these tracks are greeted like old friends by the enthusiastic crowd, the evening is dominated by material from her new album, Have One on Me. Performing its title track with her band (two violins, trombone and percussion, while arranger Ryan Francesconi plays everything from the banjo to the kaval, a kind of wooden flute), Newsom's hands move as nimbly as the spiders she sings of.

It's followed by "Easy", where her lovely swooping vocals are matched by more direct lyrics: "honey, you please me/ even in your sleep". But "Soft as Chalk" recalls the old rasp, and as she yelps her way charmingly through it, her body seems to respond, head nodding, mouth twisting, shoulder popping.

After she tunes up the harp (her "persnickety instrument") we launch into "Kingfisher". Like many of her songs, its structure is complex, repeatedly shifting in tempo and rhythm. With Francesconi on the kaval, "Kingfisher" starts like a Tudor court entertainment and winds up on a Japanese-style trill.

A more accessible track, "Good Intentions Paving Company", gets a whoop of recognition. And the honey-sweetness here has a sting of self-knowledge: "I regret how I said to you, 'honey, just open your heart'/ when I've got trouble even opening a honey jar".

Last time I saw Newsom she played alone, and while tonight doesn't quite match that intimacy and intensity, the lively arrangements have an exhilarating quality that still delivers a delicious shiver.

Newsom is supported by one of her "favourites", Roy Harper. He comments that Newsom is "one of the most beautiful women I've ever seen, performing some of the best music you're likely to hear on this planet." Few present would disagree.