I only heard her once live - at the Barbican Hall in London, already quite late in her career. She was singing a Mozart programme, which is repertoire not usually associated with her. I think it would have been Vitellia's Non piu di fiori (she sang the role at the Met in 1984) and Exsultate Jubilate, as well as maybe some concert arias. I can't quite remember. I do remember that the voice sounded quite large in the hall, but this might have been more down to the fact that it had great penetration and sounded as if it would cut through much heavier orchestration.