YouTube: Play Only Audio v1.0.5
Adds a "VIDEO: ON/OFF" toggle button to the YouTube video player to allow you to quickly and easily turn off video of any YouTube video and play only its audio.
This extension works on individual tabs meaning you can disable video playback in one window or tab and have it enabled in another.
Note:
Ad-blocking software might affect the functioning of this extension.
This extension may not work with live videos.