I am hacking together some tools to help me mix my songs. I started with Master Muter (https://github.com/Neurogami/renoise-ng/tree/master/lua/com.neurogami.MisterMaster.xrnx, renamed to Mister Master) which adds a Gainer device to the master track; this can then be switched on and off using OSC.
I decided would like to be able to use OSC to toggle mono/stereo master output, so I now have my tool add a Stereo Expander device.
When the device is added the Lua code sets “Expand” to 0 (i.e. mono). But I also want to set “Mono Mix” to “L+R”. The device defaults to just “R”. I can not figure out how to set this to “L+R” using Lua.
I ran some code posted at https://forum.renoise.com/t/using-a-for-loop-for-good/33741 to get a list of parameters for all device (very handy!).
This is what I get for Stereo Expander:
[Audio/Effects/Native/Stereo Expander] => table
 => Expand
 => Surround
Is there an API call for this device that will let me change the mono mix value?