Ducking audio input instead of cutting stream?

I like to know if I can change some part of LibreTime code to do and “audio ducking” (lower the volume of the main stream) instead of cutting and replacing the incoming /master

Which part of the code is in control of the change in the incoming “/master” signal and the main stream?
Is possible using liquidsoap?

In my head,
the ideal is be able to connect to some mountpoint and do and audio ducking, but if i want a total cut, using another mountpoint

For example:
/master : Usual beheavior, cutting the main stream and replace with the incoming stream.
/master+ : Lower the volume of the main stream (-10 dB) and mix it with de incoming stream.


Some days ago, I suddenly delete and move some songs in the current playlist,
the weird part is that two songs start playing in the stream at the same time, mixed together
So I only can think is this is possible also with the input stream (some kind of mixing)