Lensky’s arioso from Act One of Onegin; the clip wanders off into something that isn’t Tchaikovsky, but is equally wonderful. Sergei Lemeshev in an old Soviet movie. Real culture and real singing, which reminded me of this old post.
[Postscript, January 1 2015: clip has been removed. The movie was Muzykalnaya istoriya, Музыкальная история, Music Story, 1940. Watch it in full here. The extracts were from 44:50 onwards and 22:25 onwards.
The arioso was also sung by Lemeshev. The clip below is a recording of it by him from 1937. Or that is the date given by YouTube. He sang in the famous first-ever recorded Onegin at the Bolshoi (live?) in 1936.]