Dwarfed by her huge Celtic harp, Joanna Newsom played a rare solo show in London on Sunday. Addressing the crowd with wry non-sequiturs and apologetic banter, the 26-year-old American singer-songwriter no longer comes across like an otherworldly pixie princess, although her exotic folk-pop confections still sound like secret portals into dream landscapes.

Earlier that afternoon, Newsom had played at Latitude Festival in Suffolk. Her evening show in London drew from much the same set list, but reshuffled and expanded to fill 90 minutes.

Both shows opened with the rippling reverie Bridges and Balloons and the expansive Emily, a lovely pastoral word-painting and offbeat homage to the singer's sister. Songs named after female names are a Newsom speciality, which she further demonstrated with the shiny, fragile Sadie and the grand, verbose, shipwrecked sea shanty Colleen.

Full of angular asides and courtly flourishes, the latter tune is a sprawling maritime epic that confirms Newsom's literary leanings. There were distant echoes of Coleridge in this surreal tale of ancient mariners and sea changes, but also of Jonathan Swift, Edward Lear and Shakespeare's The Tempest.

Midway through the set, Newsom swapped her harp for a grand piano, on which she played a clutch of new songs.

The first sounded like an antique gospel spiritual, with its quasi-biblical lyric celebrating the sweet, clear, healing waters of a magical spring. But the others seemed a little flat and unfocused, with the singer straining to reach shrill highs and smouldering lows.

At the keyboard, Newsom sacrificed some of her uniqueness, tinkling away at fairly conventional soft-rock ballads in a Tori Amos or Kate Bush tradition. That said, the newest of her half-finished tunes was an alluringly languid saloon-bar waltz haunted by the ghost of Patsy Cline, while her upbeat tumble through the sardonic Inflammatory Writ also packed a playful punch. Returning to her harp once more, Newsom immersed herself in the perfumed, shimmering beauty of Peach, Plum, Pear. Another new composition, Esame, sounded mournful yet strangely rhapsodic.

In small bursts, this was a spellbinding show. But taken as a whole, it lacked the variety of tone and texture that Newsom can muster when playing with a small backing band or full orchestra. She remains a rare bloom indeed, but her delicate chamber pieces wilt a little during prolonged exposure to fresh air.

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