Maria Callas took up Odabella’s aria “O nel fuggente nuvolo” from Verdi’s Attila for a handful of recording sessions in 1964 and 1969.
If the YouTube information is to be believed, this recording is from 1969, possibly with material from 1964 spliced in. (I don’t often revisit Callas’s very late recordings, so I cannot say for sure.) Her sound is raw at certain moments, yet how splendidly she shapes Verdi’s music and makes it into a living, breathing thing.
Consider that Philips recorded a complete Attila with Ruggero Raimondi and Cristina Deutekom a scant four years later. If only Callas had taken part in that project!