A modulation-signal generator circuit generates a modulation signal having a time width corresponding to tone data that is input. The modulation-signal generator circuit includes an output section outputting the modulation signal and a control circuit. The output section is controlled so as to set the height value of the modulation signal to a predetermined height value during a first period in a period during which one modulation signal is output and is controlled so as to set the height value of the modulation signal to a height value higher than the predetermined height value during a second period. The control circuit sets a maximum time width which is available as the first period, and sets the maximum time width in accordance with a signal generated based on an instruction of a user or sets the maximum time width in accordance with a signal indicating the characteristics of the tone data.