The line snaking around the Barbican's foyer in the hope of returns for this long sold-out event suggested that Joanna Newsom's arrival as a serious contender has surprised even the most hawk-eyed trend watchers.

But ever since Mary O'Hara retired, the audience for singing harpists has been unpredictable.

The Californian's first hour was fabulous. Accompanied by the LSO, she swept through her second album, Ys.

A fascinating mixture of folk, outsider music, avant garde and pop, the five lengthy but curiously threatening madrigals overflowed with intricate melody and counter-melody and tongue-twisting, shape-shifting lyrics.

She sang in a voice as expressive as Kate Bush and bashed her instrument like a woman in a hurry.

Delighted to be stretched by Van Dyke Parks's innovative arrangements, the LSO gave her material, particularly the stunning Cosmia and the triumphant Emily, the depth they deserved.

It was music like you've never heard before, from another, better planet. If she'd stopped there, it would have been the concert of a lifetime.

Instead, Newsom returned for another hour, sans orchestra. For all the twists and turns of Bridges And Balloons, she suffered by simply not being as stunning as before.

Next time, she'll surely start with the good and finish with the astonishing.