Set volume control for each app individually I'm capturing video with Final Cut Pro and I'm hearing the sound of the recording.

I would like to use the computer for other things while capturing.

How can I disable the sound for a specific application?

Please don't give solutions for paying apps.
I think SoundBunny is an app which works for this. 
Link:
https://www.prosofteng.com/sound-bunny/
However it is paid $10 but there is a free month trial which you might be able to capture your video in time in that month. I haven't tried the app myself but it seems ok from the screenshots.