When someone plays it by ear, means to act according to the circumstances; improvise.
It can be said when someone is asked a question and uncertain of how to answer it.
To let things go as they may.
1. It’s Friday, what are you doing tonight? I don’t know, I’ll play it by ear.
2. I’m not sure if I want to go bowling, I’m going to have to play it by ear.
3. If they ask for something we haven’t prepared, let’s just play it by ear.
4. The surprise party might not go as planned but we can play it by ear, the day of.
according to pleasure, as one thinks best, as one wishes, at will, improvise, make it up as one goes along, think on one’s feet, throw together, unprepared, unrehearsed, whip up, wing it