“Let’s Play It by Ear” Means “Let’s Decide as Things Develop”

“Let’s play it by ear” commonly means that we will not lock in the plan yet; we will decide or adjust it as the situation develops. It is natural in Australian, British and American English. The tone is relaxed and flexible, although it can also sound non-committal.

A: Should we book an outdoor table?
B: Maybe not. Let’s see what the weather’s like and play it by ear.

It is close to “wait and see”, but the emphasis differs. “Wait and see” focuses on postponing judgement while more becomes known; “play it by ear” focuses on adapting what you do. If someone needs a firm date or a clear responsibility, this expression alone may be too vague.

https://dictionary.cambridge.org/dictionary/english/play-it-by-ear