Dame Janet Baker singing the role of the Angel in Elgar's Gerontius : Part II No 8 "Softly and gently" under Sir John Barbirolli. To think she had to audition for the part !!!. Then again there is Elgar's Sea Pictures, which nobody has managed to perform it better IMHO.
There is an anecdote that Janet likes to relate. Apparently she and her husband were listening to a "young" mezzo singing Wagner on the car radio. She thought she was "rather good" and the announcer confirmed that it was indeed Janet Baker singing !!