Malena Ernman, Wigmore Hall, London

Anyone who saw Malena Ernman as the androgynous Prince Orlofsky in Die Fledermaus at Glyndebourne a couple of years back won't have been surprised by anything that she sprang at this Wigmore show. The tall, very blonde, very svelte Swede dresses to kill and sings to resuscitate.

The voice is gender-defiant, the manner oddly asexual. The predominant vocal colour is lush contralto - and what a great sound, a great colour, it is. But there's also a butch bass-baritone and ditzy coloratura soprano at the extremes, and she just loves bringing them out to play. Ernman is more than just a singer; she's an impressionist, a character actor, a "turn" - and therein lies her problem. She badly needs a director.

The evening began in denial, with a cool, understated, almost dispassionate account of Schumann's most personal song-cycle, Frauenliebe und leben. Her pianist, Bengt-Ake Lundin, set the tone with a hesitant, clipped account of the celebrated opening - and closing - theme. Ernman proceeded as if events had long since overtaken her, lingering only over the arrival of the wedding ring and the aftermath of her beloved husband's death, where she flattened her sound to produce an even more alarming dissonance with the keyboard. This was striking.

But then, out came the funny voices and facial contortions for the menagerie that is Ravel's Histoires naturelles, and the wackier side of Ernman's platform persona went into overdrive. She should trust the words more. They don't always need illustrating; you don't need to play a line such as, "I want to bite my initials on a sailor's neck", from Gershwin's "The Lorelei" (her encore). It was interesting to me that in her native language, in three songs by Emil Sjogren, the words flowed freely and unimpeded.

The performer, the mimic, the actor in Ernman was altogether better accommodated by William Bolcom's 12 Cabaret Songs, and the motley characters - the good, the bad, and the very ugly - passing through them. Best of all was "Amor", the song equivalent of a wolf-whistle. Like all good actors, Ernman came up with several wicked ways of saying - and meaning - that most provocative of words. But "Amor" apart, it isn't always advisable to go all the way. A talent this big sometimes needs taking in hand.

The jazz set, later the same evening, was not a success. It isn't enough just to love the material; you need to inhabit it. Ernman is more of a sitting tenant. She takes elements of the style - blues, swing, scat - and applies them liberally. But it isn't about application, it's about feeling. Her relatively "straight" rendition of "Maybe This Time", from Cabaret, was a classic case of a great song in the wrong place at the wrong time.

And if I were Ernman's director, I would advise her against self-deprecating jokes such as: "So, you haven't left yet!". It's a sure way to make them wish they had.