Provided are a method, computer storage device, and tone control device for generating tones with a vibrato effect. A determination is made of a key depression interval comprising a difference of a current time of a current note from a previous time of a previous note. A performance mode is set to a single tone mode, in which only one note is generated, or a polyphonic mode, in which multiple notes are simultaneously generated, based on the determined key depression interval. The tone is generated to output the current note with a first modulation magnitude in response to determining that the performance mode is the single tone mode. A tone is generated to output the current note with a second modulation magnitude in response to determining that the performance mode is the polyphonic mode, wherein the first modulation magnitude is greater than the second modulation magnitude.