To provide a method for controlling a sound effect signal corresponding to a musical sound signal of a guitar or the like in the mixing of the musical sound signal with the sound effect signal.

The method includes: a musical sound signal input process 8 for inputting the musical signal; a sound effect input process 6 for inputting the sound effect; an envelope extraction process 10 for extracting the envelope of the value of the musical sound signal and that of the absolute value of the musical sound signal; a control parameter calculation process 12 for calculating a control parameter based on the envelope and either of sensitivity that is the increment ratio of the control parameter to increment in the envelope or a threshold that is a threshold value where a curve having nonlinear characteristics in the control parameter to the input level or the control parameter follows the input level; and a sound effect control process 14 for controlling the sound effect based on the control parameter.