LPX and Roland Sound Canvas VA

I just got the Sound Canvas VA plug-in, having used a hardware version a long time ago. It has some useful instruments and drum kits which can be accessed on different MIDI channels. I've been able to set up a jazz combo of bass, drums, tenor sax and piano on MIDI channels 1 2 3 and 10, but I've had to use four separate instances of the plug-in to do this and a track for each. Is there any way to access the multiple instruments in one instance of the plug-in from my four tracks? I can't see any way myself but, in theory, it should be possible if the four tracks were preceded by a MIDI channel event. I don't know how to do that, can anyone help?