change your tune idiom disapproving
（尤指为了好处而）改变看法，改变论调
to change your opinion completely, especially because you know it will bring you an advantage
He was against the idea to start with, but he soon changed his tune when he realized how much money he'd get. 一开始他反对这个主意，可是等他意识到自己能赚到那么多钱时就立刻改变了态度。