What is a musical ear?

Answer 1

Also known as Musical Ear Syndrome, it causes signals to be sent from the brain to the ears more often than normal, meaning the person can hear sounds when they are not actually there. This can be the result of hallucinogenic persistent perception or listening to the same music or sounds very often.

Answer 2

To play by ear means that you can hear a song and then pick up an instrument and be able to figure it out easily. To have an ear for music means that you're a talented at the art of music and can play and sing just about any song that comes your way :)