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.
3rd Party Loopback Audio Virtual Devices/Drivers
- Blackhole - free full version
- Background Music
- Rogue Amoeba Software: Loopback - trialware, pay software
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.
Another possible option as a loopback is "Background Music"
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.
- In the QuickTime Player app on your Mac, choose File > New Audio Recording.