[RWP] using side-chain on ReaComp as ducker

[Patrick Perdue]

Hello all:

Reaper and I have not been friends, really, from the start, especially 
given I can't set it up the way I'd like, due to the lack of ability for 
us to change the master track routing, since ReaAccess doesn't show it 
on it's virtual interface for some stupid reason. Still pretty bummed 
about that, but I've found some temporary workarounds for it, I.E. 
creating another fake master track, and sending all relevant tracks to 
it, effecting as necessary, or bypassing the master track and using 
individual returns on my audio interface (works OK until a project needs 
to be rendered, then it's kind of messy.)
As a result, I haven't really used it all that much.

However, it looks like I may not have access to my studio for a little 
while if things go as planned. So, I want to set up a portable 
broadcasting solution using a laptop, Reaper, my Zoom h4 recorder for a 
mic preamp and headphone output, Virtual Audio Cable, Asio4All (since 
you can't use multiple interfaces in tandem through DirectSound,) a VST 
Icecast/shoutcast streaming plugin, a few instances of a gate and 
ReaComp and/or other suitable compressors on individual tracks, etc.

I want to use side-chaining on at least one of the ReaComp instances, 
maybe even two of them, but can't figure out for my life how to get 
audio sent to inputs 3/4 of the compressor from other tracks to make 
that happen.
I get that you need to change the number of track channels on the track 
where the compressor has been inserted to four, and to change ReaComp's 
detection input to aux left/right rather than main left/right, but I 
don't know how to make other tracks send to 3/4 on the compressed track. 
The only thing I see about channels at all in any of the routing things 
when setting up sends or receives (which, as far as I can tell, are 
exactly the same thing in reverse,) are midi channels 1-16, not audio 
channels.
I found a video on Youtube that made it look pretty easy, and it seems 
I'm only missing this very obvious step. It looks like there should be a 
drop-down list of audio channels of the source track somewhere, but I'm 
just not finding it.

Anyone here have an idea what I'm overlooking?