With context these can mean different things. You might also play a piano, or hire either a player piano, or a piano player. If you are answering which instrum

With context these can mean different things. You might also play a piano, or hire either a player piano, or a piano player. If you are answering which instrument you play, it's the former, but if we are talking the profession it's the latter, because you don't say then that you play a piano.