That's probably easier said than done. When I was in high school my band director taught several of us to hum harmony to what we were playing, neat trick at the time. I have noticed though in the last couple of years that during practice I find myself humming what I am playing. It is not all the time and I have been trying to get a handle on just when I do it, I really haven't noticed it at big band rehearsal or during performances but then it might be hard to hear. I have tried to see if I do it when I am sight reading but when I concentrate on it I don't do it. The mind is a terrible thing!