Music: Pinch Hitter

To most unknown singers the chance never comes in a lifetime. But it came to short, plump-cheeked, 23-year-old Astrid Varnay—the chance to stride the stage of the Metropolitan Opera in a big part. Soprano Lotte Lehmann fell ill, Soprano Varnay donned the blond wig and nightie of Sieglinde in Wagner's Die Walküre. Though she had never appeared on any stage, she sang that hapless housewife's role with such easy assurance that critics all but ho-yo-to-hoed.

That happened a fortnight ago. Last week an even bigger part fell vacant —Die Walküre's Brünnhilde. Helen Traubel, herself pinch-hitting for Kirsten Flagstad (immured in Norway for...