Nothing more to say...

how many of these threads do we need.....

How many posts like mine do we need? Cheers!

That line about sidechaining is not new, it's been on the REAPER website since version 2.4. It refers to audio signal driven parameter modulation. (What is new in REAPER 4 is that you can drag one track's IO directly onto an open FX GUI, which will automatically create the destination channels 3/4.) Then move a plugin knob, press the Param button, select Parameter modulation, and check "audio control signal." That will drive the plugin knob with the audio from the sending track. But like I said, that's not a new feature, and the web site text about it is not new either.

Cheers Schwa, I get it now.