Track or live singing?
When I saw Victor Victoria first run in the theater, I could have sworn that the stars were singing live -- their matching to a vocal track was that good.
Over the years I have looked for tell-tale signs of track vocal where you can see a momentary lag in mouth movement against vocal track and I STILL CAN'T.
I believe that Robert Preston's final opus of Shady Dame for the most part is live singing.
Really, all of the matching to vocal track is SO TIGHT that it looks as though the stars on all the numbers are singing live. Plus the energy in the vocal completely matches the action and energy on screen.
Now THAT is professional skill.
No question one of my favorite movies of all time and I could see VV, My Favorite Tear, Local Hero and Some LIke It Hot every day all day.