You can't get what you want just with MIDI-Thru on your devices?
The reason why is that the only device that has a midi thru is my CM-64, which must be turned on for the midi thru to function. My MPU-401/AT + SCB-55 and my CM-64 will be output to the same speakers, but I will only output one device at a time. If I send the midi destined for the MPU-401/AT + SCB-55 through the CM-64, the CM-64 will also output very wrong sound and vice versa.
Perhapsn an audio switch box might be better, if it can properly suppress the audio signal of the module that I don't want to hear so that it doesn't interfere with the sound I do want to hear. Anyone know where I can find one of those.