[sing a different tune] or [whistle a different tune] also [sing a new tune] {v. phr.}, {informal} To talk or act in the opposite way; contradict something said before.
* /Charles said that all smokers should be expelled from the team but he sang a different tune after the coach caught him smoking./
Syn.: CHANGE ONE'S TUNE, DANCE TO ANOTHER TUNE. Compare: LAUGH OUT OF THE OTHER SIDE OF ONE'S MOUTH.