Background Tab Audio Fader от Jasohug

BTAF is meant to designate a single tab to lower or mute it's volume when another tab has audio playing, meant for things such as having a designated tab with background music to play as you browse videos or clips on other websites, and fade out/mute/lower when another tab plays audio for clarity, with the tab resuming once all other sources of audio from other tabs has stopped.

The Add-On does NOT stop the audio source from playing, only mutes/lowers it, so videos will continue to play in the primary tab as it is muted.

Customization options include designating which tab to be the Primary Tab, ability to set Primary Tab volume, set fade-in and fade-out delay time in ms, setting volume for tab if Lower Volume option is selected, and how much the volume is increased/decreased by when fading in/out.