"I appreciate the beaver," says KD Lang, returning for her encore. The beaver in question is the stuffed, cuddly variety, thrown to her by a fan. But in front of this audience, which is by no means entirely female, what would normally be a double entendre becomes a simple statement. The kind of woman who is always going to be called handsome, and certainly the only out, butch lesbian singer to achieve significant international success, Lang knows how to work her constituency.

She sings exquisitely. The long, pure, sustained notes with which she elegantly navigates each tune are the polar opposite of the gruesome melismatics of modern soul-influenced pop. She is every bit the equal of the classic singers of the 1950s and 60s who could sing country, pop and jazz with equal style and conviction. But everyone else on stage - Lang's four-piece band, the London Philharmonic - seems to be going through the motions. When Lang disappears after only 12 songs (including encores) in a brief 70 minutes, it's hard not to feel she is short-changing her adoring fans.

Her material is beautifully turned out, but overfamiliar: it is lifted by the few songs she plays from her fine current album, particularly two by fellow Canadian Jane Siberry. The Valley and Love Is Everything are minutely detailed, peerlessly graceful swells of compassion, wonder and heartbreak, and Lang sings like she loves them with gently devastating force.

But while she says she is "thrilled" to be performing with an orchestra (this is her first orchestral tour), the arrangements are at best lacklustre and at worst barely audible. For a long time, the tension in Lang's music has come primarily from her sexuality. It is no longer enough.

· At Colston Hall, Bristol, tonight. Box office: 0117- 922 3682. Then touring.