Do you play a musical instrument? Have you ever sat down at a piano and pressed the keys until you hear a familiar tune? If so, then you understand the literal meaning of this expression.
To play an instrument by ear means that you create music without any written instructions or score — you simply play different notes until they sound like a song you know.
In daily conversation, however, you might hear people use this expression in ways that have nothing to do with music. To PLAY IT BY EAR means TO PROCEED WITHOUT A FORMAL PLAN OR SCHEDULE.
For example, if you and your friends want to get together for dinner, but no one knows exactly when or where you will meet, you could say, “Ok, we’ll just play it by ear,” meaning you’ll text or call each other later and make plans as you go.
Other expressions can be used in the same way, such as “wing it” or “fly by the seat of your pants.” They essentially mean the same thing: to take action without a specific plan or strategy.