sing a different tune 改变调子；转变态度；唱反调；变卦

【例句】
He'll sing a different tune when he has to earn his own money.
当他必须自己去赚钱时,他就会唱反调了.

I bet Dan will sing a different tune when he finds out what the salary is.
我打赌当丹发现薪水是多少的时候，他就会改变态度了。