I would save "swan song" for The Whales of August, that unbelievable film with Lillian Gish, Ann Sothern and Vincent Price as well as Bette Davis.
She recorded Cole Porter songs, and "They're Either Too Young or Too Old." She is actually a good singer, this was not staged or really coached, as you can see her counting the beats when not singing. Her pitch and rhythm are utterly solid. Grace was not her thing, of course, that was Olivia de Havilland or Celeste Holm.
I think Glenn Close and especially Gena Rowlands are very much in her category nowadays.