Specifically let's say one audio source from one tab and another audio source from another tab that can be played at the same time without automatically pausing one of them when the other starts playing.
When both audio/video sources are on the same tab (like one web page that has 2+ MP3/MP4/Webm/etc. files), FF can play them at the same time, which is great. But this app would be a million times better if users can play audio from at least two tabs at once.
I appreciate the hard work the FF team has put into this app, it's my favorite browser by far. If they could add this feature it would be a dream come true. Thank you.