I'd say the trick to "playing by ear" is to learn to improvise over things keeping in mind the key you're playing in. I think there's this misconception that "

I'd say the trick to "playing by ear" is to learn to improvise over things keeping in mind the key you're playing in. I think there's this misconception that "playing by ear" means you hear a song once and then you play it note for note. In theory, this can work if you have a great memory, but really the trick there isn't some musicianship skill, it just means you can remember how the song goes better than other people, then when you sit at your instrument, you kind of have an idea of where it starts and finishes and go from there. I have a terrible time remembering songs by rote memorization, but as long as I can remember where it starts, goes and ends I can probably pick it back up, just by remembering the chord the song starts on. It's because I've improvised a ton in different keys and I know my pallet of notes to choose from. I'm familiar with what chord colorations are available and I know how melodies tend to move. Do I hit wrong notes? Sometimes, but I guess if I know they're wrong and correct them I'm still playing by ear, but I'm also playing a little bit by theory too, the theory kinda shrinks the constraints of playing by ear. If I see a chord progression, let's say G-C-D, I don't remember it that way. I remember it as a I-IV-V progression in the key of G. It helps.