"When I sang too much Wagner, the voice got dark, without shine, and heavy."

He sang Wagner at La Scala with Toscanini.

Rachel Nicholls: "No-one ever tells you you're ready to sing Wagner - you have to dare to try for yourself."

To sing Wagner properly, one trusted adviser insisted, you need even more purity of line than for Verdi.

It is unclear whether and when Vezzani sang Wagner on stage, but he recorded a number of pieces from Lohengrin and The Ring.

So, for some critics, including this one, the slight Latinate tinge in Mr. Domingo's sound when he sings Wagner actually enriches his characterizations.

And I went to Los Angeles to hear Domingo sing Wagner with Gergiev, which really broadened my horizons.

He couldn't even be persuaded by Sir Georg Solti to sing Wagner because he felt didn't suit his voice.

"I don't know anybody who sings Wagner who doesn't want to try," he replied.

Had she lived longer, it might have been a different story - Karajan wanted her to sing Wagner at Bayreuth.