What does "play it by ear" mean — and why is it funny?

informal

Meaning

To deal with a situation as it develops, without a fixed plan.

Where it comes from

From music, where to 'play by ear' is to perform from memory and instinct rather than from written notes.

Why it is funny

The mild humor is the calm confidence it borrows. Facing the unknown becomes like a musician casually performing a tune with no sheet music — improvising, listening, and trusting it will all come together.

Used in a sentence

"We haven't booked anything for the trip — we'll just play it by ear."