I know that if I use MMV 2 in Cakewalk SONAR 3 as an effects processor in the audio channel of a source, not as a separate midi instrument, then MMV 2 somehow knows where to pick up the external sound from. There is an unfortunate side issue in that when I use MMV 2 in this way, there is no way to tell the MMV 2 instance where to pick up MIDI instructions from.
This whole scenario seems to reflect an architectural hole in music software in general. In a perfect world, SONAR would be able to see virtual audio channels offered as devices by MMV 2 and use them as it would use the audio channels provided by the sound card driver. The programming costs of this I suspect would be big.
I hope that I am mistaken about this and that someone offers a better solution in the forum.
David Olive