play something by ear

play something by ear就是想做一件事，可是又不能确定是否可能，只好到时候看情况再说，就像中文里说的"看情况而定"!

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

我没时间为面试做准备，只好见机行事了。

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

我们周六中午见好吗?

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

我早上要办点事，所以我们到时候看情况再说吧。