“And it came to pass, when the evil spirit from God was upon Saul, that David took an harp, and played with his hand: so Saul was refreshed, and was well, and the evil spirit departed from him.” I Samuel 16:23
Don’t be confused. It wasn’t the harp alone that caused the evil spirit to depart from Saul. It had much to do with the anointed man who was playing it.