Fader operators operable manually and automatically are provided in corresponding relation to a plurality of channels. For each of the channels, a setting section can set a fade operation mode of the channel to either a first mode where a fade is enabled or a second mode where the fade is disabled. Upon receipt of a crossfade execution instruction, a corresponding fader operator is automatically operated in such a manner that each channel set in the first mode is faded in or faded out. When the fade operation mode of a given channel, which is undergoing a fade process, has been changed to the second mode, the fade process for the given channel is ceased, and the corresponding operator is changed to a predetermined operating state, e.g., state immediately before the start of the crossfade. According to another example, when a crossfade cease instruction has been given (e.g., by manual operation of the fader operator) for a particular channel which is undergoing a fade process, the process for the particular channel is ceased with the operator for the particular channel kept in the current operating state.