A supporting system is provided on a saxophone for offering assistance to the player, and includes pressure sensors monitoring the touch pieces of the keys, power assisting units equipped with torque motors provided for the keys and a controller connected to the pressure sensors and the power assisting units; a conversion table for depressed touch pieces and another conversion table for released touch pieces are prepared in the controller, and different relations between the finger force and the amount of current to be supplied to the torque motor are respectively defined in the conversion tables, respectively; the amount of current to be supplied is read out from the conversion tables depending upon the increase and decrease of finger force so that the player quickly closes the tone whole with the padded cup without curious key touch.