The utility is greatly limited by the inability to control a tab's volume BEFORE the audio begins. Also, the lack of persistence means that you're in a race with the noise controls if you visit an offending page with any frequency. Can't just set it once and forget it.
"...control a tab's volume BEFORE the audio begins." Fixed. That was intended to work but broke at some point. Now the 'main' tab should always be visible, sound or no.
"...set it once and forget it." Solid idea, should work now.
