A performance apparatus 11 extends in its longitudinal direction to be held by a player with his or her hand, and is provided with an acceleration sensor 23 for detecting an acceleration sensor value and an angular rate sensor 22 for detecting an angular rate of rotation of the apparatus 11 about its longitudinal axis. CPU 21 detects a sound-generation timing based on the acceleration sensor value. Using the angular rate, CPU 21 calculates a rotation angle of the performance apparatus 11 made about its longitudinal axis in a period from a first and a second timing, wherein the first and second timing correspond to starting and finishing of swinging motion of the performance apparatus, respectively. CPU 21 determines to increase or decrease a sound volume level, in accordance with the direction and amount of the calculated rotation angle, thereby adjusting a sound volume level of musical tone.