Roocroft / Martineau, Queen Elizabeth Hall, London

Amanda Roocroft was little more than a college student when she first drew international attention in such stage roles as Sophie in Der Rosenkavalier. Her voice was always precocious, but it took time for the artistry to catch up with the technique. Motherhood did that for her. But what I wouldn't give now for a little of her former purity.

Recitals tend to expose, to amplify, all that is suspect in a vocal technique; there is no orchestra to cover the blemishes, no big theatre acoustic to accommodate excessive vibrato. Roocroft is really affecting on stage, and the roles she has been developing of late have taken account of the big changes in her voice. The bright, widening vibrato, the new-found steel in the voice lends itself to the Slavonic repertoire. She will make a wonderful Tatiana in Eugene Onegin, which I see she is preparing. But she needs to stop now and take stock of those changes if she is to be an equally affecting recitalist.

This was not a happy evening. Some of her choices were admittedly unwise. To start with, Debussy's Ariettes oubliées would stretch the most refined of techniques. These "forgotten airs" suggest a certain remoteness. Their ethereal quality tempers rapture with restraint. At the very least, Roocroft needed to rein in the "operatic" sound and fury, curb the emotion.

She sings very far back in the throat. The French repertoire demands a more forward production - a narrower, more focused timbre. She made precious little of the words (when they were accurate); she didn't capitalise on their seductiveness. The very first song speaks of "languorous rapture". But you need to understand the style to convey that.

Her dynamic range was limited to mezzo forte and above. Where were the elusive pianissimi? Where were the half-shades? It fell to the masterly Malcolm Martineau to find all of this in the keyboard writing.

Roocroft's Liszt set should have been more successful, and was, though again (sucker for punishment) she chose French settings. At least that ravishing mélodie "Oh! Quand je dors" ("Ah! While I sleep") unlocked her best qualities - a soulfulness writ operatically large. We heard more where that came from in the Strauss selection. Roocroft's shimmering legato came into its own in "Gluckes genug" ("Happiness Enough"), and the maternal warmth came naturally to her in "Meinem Kinde" ("To My Child"). But for all the energy and vitality of "Herr Lenz" ("Lord Spring"), leaping through town in his "bright blue stockings", the sameness of the delivery - over-pressed and overlit - grew tiring on the ear.

The lighter touch simply eluded her. Removing the coat part of her gown was presumably designed to lend Britten's Cabaret Songs a touch of informality. But she looked anything but informal perched on the concert-hall equivalent of a bar stool. She could use the discomfort for the uneasy train-journey of "Calypso" (though most of the words were a blur), but it only seemed to intensify the heavy weather she made of "Tell Me the Truth About Love", Britten's amusing take on Cole Porter. A lyric like this isn't funny if you keep telling your audience that it is.

Recitals can leave an artist cruelly exposed. The chilly ambience of the Queen Elizabeth Hall and the consumptive winter audience didn't help. But Roocroft needs to think again.