Playit by Ear

To fiddle with something, you need make some adjustments to the instrument so that it sounds right. So if someones change their tune, ah, what does that mean? And then we have a second one, which also is related to music. Playit by ear. I'm always so impressed by people who can do that. Just like listen to something and then be able till i play the note on a guitar or a piano without having to see anything.