Scott (or is it rockstar_not - I'm not familiar with forum etiquette),
Your mixing tip re backing off the lows makes good sense and it is not something that had occurred to me thus far - thankyou.
As to your question, my synth is the plug-in version of the one that gets bundled with Biab: VSC DXi. It seemed (and still seems) sensible to follow the path of least resistance with regard to technical stuff I know little or nothing about, and the sounds of the basic rhythm section instruments are OK for my present purposes.
Which is not to say that I intend to remain technically ignorant and unaware of alternatives, more a question of first things first. Suggestions and pointers-in-the-right-direction are welcome.
Language like "a unique instance of the synth" is a bit daunting to me but rharv's correct assumption about using 'reroute all MIDI to DXi' and directions about where to look (thanks again rharv) got me over the line, and the job got done.
Curious though, now that I can apply effects to MIDI output, why would I be wanting to convert to WAV and treating the resulting audio track instead? I'm thinking that keeping things flexible for as long as possible is, generally speaking, a good thing.
As for distinct channels for each MIDI track, I'm in the habit of doing that on account of having had a really terrible time with MIDI channels left set to 0 when I first started with RB. All sorts of unpredictable and wildly frustrating behaviour was going on which diminished greatly when I decided on "every track different, NO zero". Is this typical, or possibly just to do with the particular way I was going about things?

Clinton