Here’s a nifty little tool that lets you record sound on Ubuntu Linux. You can record your own voice for voiceover or you can record streaming audio from tools like Rhythmbox and VLC.
Commands to install the audio recorder tool in Ubuntu based distributions:
sudo apt-add-repository ppa:audio-recorder/ppa
sudo apt-get update
sudo apt-get install audio-recorder
Text form of the video: https://itsfoss.com/record-streaming-audio/