play something by ear 

play something by ear就是想做一件事，可是又不能確定是否可能，只好到時候看情況再說，就像中文里說的'看情況而定'!

I didn't have time to prepare for the job interview. I will have to play it by ear.

我沒時間為面試做準(zhǔn)備，只好見機(jī)行事了。

A: 'Are we meeting at noon on Saturday?'

我們周六中午見好嗎?

B: 'I have to run some errands in the morning, so let's play it by ear.'

我早上要辦點事，所以我們到時候看情況再說吧。