play something by ear
play by ear
1. To play a piece of music without referencing sheet music or a recording. In this usage, a noun or pronoun can be used between "play" and "by ear." Wow, George is such a talented piano player! The way he can play pieces by ear after hearing them just once is so impressive! Just because he can play by ear doesn't mean he's a great songwriter.
2. By extension, to make decisions about what action to take in an adaptive, flexible way, based on the circumstances. In this usage, a noun or pronoun can be used between "play" and "by ear." A: "Are we meeting at noon on Saturday?" B: "Around then. I have to run some errands in the morning, so let's play it by ear."
play something by ear1 perform music without having to read from a score. 2 proceed instinctively according to results and circumstances rather than according to rules or a plan. informal
2 1992 Paul Auster Leviathan The only condition was that Sachs arrive at Maria's house promptly at ten o'clock, and from then on they would play it by ear.