Forget about "listening to the overtones". It is almost impossible to listen to our own sounds because the player does not get what comes out of the bell. Getting a fat sound is most easily accomplished by playing with those better than you. When you play duets with a superior player, all of a sudden things make sense - we don't even need to talk about them. Sympathetic vibrations with a piano or other resonant instrument only need "loud" to get going. They are no sign of quality. When more overtones are present, our sound is "brighter". We cannot control which overtones get stronger with our chops. That can only be done with hardware. Our chops when they are well trained and not pinched off, allow "all" the harmonics to flourish.