In the multi-timbre states in which musical tones with various timbres are outputted or imputed simultaneously and in the non-multi-timber states in which musical tones with a single timbre are outputted or inputted, the most suitable state of transmitting musical tone data is provided. When the non-multi-timber states is selected (step 12), the zones “1” and “2” turn into the in-communication states (INT) and the zones “3” and “4” turn into the out-communication states (EXT). When the multi-timbre states is selected (step 12), all the zones/timbres turn into the both-communication states (BOTH) (step 13). The both-communication states provide said in and out-communication states simultaneously. In the out-communication states, tone data are sent to the external apparatus connected to the musical tone (internal) apparatus. In the in-communication states musical tone data are sent only within the musical tone (internal) apparatus.