A talented actor and a pleasant man by all accounts.
He was rather splendid as Chang in The Undiscovered Country.
He was famously dubbed (much to his annoyance) in "The Sound of Music" but this is the unused sound recording of Plummer actually singing in the film:
https://youtu.be/obEm1Mqm7C0Not as good as the singer who dubbed him in a technical sense, but in an emotional way I think Plummer's singing suited the song better.
