Here is a neat example of overtones on a piano. Depress the G above middle C (without sounding it) to remove the damper from the strings and hold the key down. Then hit the C below middle C very hard. You will then faintly hear the G you are holding down. The G overtones from the C that was hit are causing the G strings being held down (undampered) to vibrate in sympathy.An example of overtones and sympathetic vibration in one. The C will generate the following overtone series C |C G | C E G (bar denotes a new octave) The 1st G in the series will cause the G strings, undampered, to sound. For what its worth, Bill Pirkle