The OPERA isn't over till the fat lady sings
Attempts to determine the identity of the diva concerned have been inconclusive.
1978
Washington Post
13 June B1
The opera isn't over till the fat lady sings …One day three years ago, Ralph Carpenter, who was then Texas Tech's sports information director, declared to the press box contingent in Austin, ‘The rodeo ain't over till the bull riders ride.’ Stirred to top that deep insight, San Antonio sports editor Dan Cook countered with, ‘The opera ain't over till the fat lady sings.’
1980
Record
(OUP) Dec. 8
Do not relax your vigilance in the fight against the punk paperbacks …‘The opera ain't over 'til the fat lady sings.’
1988
Black Star Murders
viii.
As soon as the big blond Brünnhilde finished, it was over. All I could think about was the classic line about the opera never being over until the fat lady sings.
1992
Independent
11 Aug. 7
‘You know, they say that the show's never over until the fat lady sings,’ Mr Bolger said. ‘Well, I think it was her was we heard warming up in the wings this week.’
finality