How to stop audio through on a synth plugin?

Development
1

I am writing a synth that expects audio IN, problem is, the audio also goes through the synth to the output.

I also tested with another JUCE synth (octasine) and the same happens, here are the steps to reproduce:

Open Reaper DAW
Insert a JUCE synth into a track
Insert an audio clip on the same track
Play

The audio goes through the synth even though I am setting every buffer sample to a custom value, clearing the buffer has the same effect.

In fact this happens with any VST synth in Reaper, question is then, how do I make a sidechain synth? I want my synth to receive audio and write the audio buffer, not letting audio through.

Thanks a lot,

2

Found it!!

Seems like I needed to override VST3ClientExtensions in my audio processor and do:

bool getPluginHasMainInput() const override { return false; }

It seems to be working so far so good, its not working for LV2 though, probably AU neither, getting also LV2 to work would be great.