Just listening to her in Puccini and Verdi arias - For me she has the absolutely ideal voice for Puccini. And the Verdi ones are scarcely insuperior - as people have said here her Aida is phenominal... Like all the greatest voices, she has a completely unique sound, intense, silvery and rounded - I have this curious image of the sound being oval. Everything is done with an a drama that is almost over the top, but that is who she was, so it works. No one else like her, and despite her limitations, she must be counted as one of the greatest.
I never feel comfortable with her singing of Barber's music... even although she was his singer of choice and the recipient of a superb song cycle (Despite and Still), sang the ravishing soprano solo of The Prayers of Kierkegaard at the premiere, sang all of his his other songs with piano, and also recieved a magnicient operatic role from him - the sound for me is too intense and declamatory for Barber's music which to me always needs a lyric sound to be fully effective. Her singing of the Hermit Songs seems completely at odds with the subject matter, as much a problem with her delivery as the timbre of the voice. Actually, the exception is Cleopatra, in the opera Antony and Cleopatra, of which she only comercially recorded the two arias - absolutely incredible singing, and the part is tailored to her voice in every bar so could not be more suited - its probably the best thing about this recalcitrant opera.
One wonders why she never did his Andromache's Farewell (written for Martina Arroyo) which would surely have been ideal for gifts and vocal fach.