I would like to make Env or LFO, Macro etc that can connect to variables user want.
In some vst plug-ins, they can drag them to the knob with the mouse and connect them to the knob.
It seems to be called various names such as Macro, Modulation, but it look like no exact technical name. So there is a difficulty in finding a way.
How do I make it possible to connect Env, LFO, etc to variables?
It’s not like envelopes or LFOs are really “connected” to any variable under the hood. Most of the time, a modulation matrix is implemented somewhere, and depending on the user actions, some internal variables in the audio processing will use the LFOs and envelopes to modulate themselves.
Your question isn’t that clear, do you have already an audio process where you would like to add modulation functionalities ? Are you talking about the processing side or the user interface side ?