The electronic musical system comprises a keyboard that has a plurality of keys to designate the pitch, a key operation detector for detecting the operating state of the keyboard, set operator that can switch to the parameter setting state, parameter value input port to input the parameter values, pressed key count detector to detect the number of pressed keys, parameter setting program for setting the parameter value according to the pressed keys detected by the key operation detector. If one key being pressed is detected, then the parameter values are set to the value of the pressed key. If, however, multiple keys being pressed are detected, then the parameter values are set to the value of the multiple pressed keys and parameter output port outputs the parameter values that were set by the parameter setting program. The electronic musical instrument allows the user to intuitively set the parameter values with a effortless operation.