PURPOSE: To speedily vary a tempo through an easy operation.

CONSTITUTION: This device is provided with a tempo varying operation detecting device 1 provided with switches 1a and 1b for tempo setting, a tempo parameter setting device 2 which calculates and sets data for tempo setting according to depressing force information detected by the tempo varying operation detecting device 1, and a tempo information generating device 3 which generates a clock for a tempo on the basis of the tempo parameter set by the tempo parameter setting device 2. When the switches 1a and 1b for tempo setting are pressed, the speed of arithmetic for increasing or decreasing the tempo is varied corresponding to the strength of the depression of the switches 1a and 1b and when the switches are pressed strongly, the arithmetic is speedily performed to increase the frequency of the arithmetic in a certain period.