loopback
If you wish to use an audio recorder to record audio being played by another application, such as capturing audio from youtube, you can use a loopback driver.
An Audio Loopback Driver is a virtual driver that allows one software to capture audio from another software. This is an alternative to capturing from a microphone. Simply holding a microphone up to your speaker would do a poor job of audio capture.
Example loopback virtual driver for MacOS
- BlackHole - Route Audio Between Apps (BlackHole v0.2.6 virtual audio driver from GitHub)
It does not appear to be in the Apple Store. It is on GitHub.
capture
You can now capture and record with the latest version of Apple Quicktime. You will still need a loopback driver to capture from another software application.