In a digital mixer including a display, cursor controls, an
increase/decrease control, and a plurality of channel strips for
controlling parameters of input channels associated therewith, on a
control panel, the channel strips each having a selection switch, an
assignment switch is provided for assigning any one parameter among the
parameters of the input channel to the increase/decrease control, so that
where operation of the increase/decrease control is detected, when no
selection switch has been operated, a value of a parameter displayed at
the position of the cursor is changed in accordance with the operation of
the increase/decrease control, while when any selection switch has been
operated, a value of a parameter assigned to the increase/decrease
control among parameters of an input channel corresponding to a channel
strip having the selection switch is changed.