freeware to record sounds from various apps

I'm looking for a freeware that could record the sounds that came out from
various apps : can be youtube, zoom,  browser playing a website, a VLC player:
only the sound without the video/screen.

Best if the audio can be saved into various common formats.

Ideally the software is portable (ie just run without installation) but this
feature is optional.


Question2:
sometimes a few apps are playing concurrently (eg: a few youtube
videos are playing): is there any way to audio-record only for a particular
youtube (the tab that I could select to record) or it'll just record the
jumbled sounds?  Purpose is to record a specific video's sound while
I'm playing another one