Maybe its true that the only way to have the two synths play separate parts is to assign different midi channels. However, with my equipment, I can decide whether or not notes are transmitted, whether or not notes are received, whether or not midi clock is transmitted, and whether or not a device is govered by an internal clock or a received midi clock. So I do not worry about channels, I turn off transmission of midi notes, have one device transmit midi clock and the other respond to it. Whther this works for the SY77 and Triton, I do not know.