Google Chrome is the first browser to show audio indicator for music playing tabs (now Firefox Nightly has also this feature), it now lets you mute those tabs (not yet available in stable)also, you should thank Google for fixing another annoyance: stopping autoplay of media in the background tabs, Chromium team has fixed this bug : ‘Defer media playback in background tabs’.

This is a feature of Chrome 46 (which currently on the developer channel.

READ: How to Mute Multiple Tabs at Once in Chrome?

Chrome 46 postpones the media playback in the background tabs until the tab is foregrounded

What this means

If you’ve opened a tab specifically in the background, an ad or video/audio won’t play automatically until that tab is forgrounded or gains focus. “Resources will still be preloaded if indicated but Chrome will delay the start of playback until you actually visit the tab.”

defer media playback

“Videos which autoplay in the background will now have their load
deferred until the tab is visible for the first time — this avoids
autoplay during session restore and premature playback.”

SEE: Google Chrome Background Pages and Apps, How to Close Them?

YouTube concerns addressed

YouTube playlist is not part of this. Bug confirms ‘playlist type media continues to work’. 

“Once a tab / RenderFrame has ever played media before, it’s allowed to continue to autoplay/autoload indefinitely; this is to support playlist type applications.”

For you to listen to YouTube songs while working in another tab, you need to visit or open that tab once first.

Francois says “This cool feature prevents obviously user annoyance but also conserves power as Chrome will only consume power once the tab is foregrounded.”