How to integrate Audacious in the sound menu?
Solution 1:
You need to use Audacious 3.2 (currently in beta stage), that has the built-in support for the MPRIS 2 protocol needed for Sound Menu integration.
Solution 2:
It will, but I don't know how many more months or years it will take.
Audacious project lead said:
I think we're just waiting for a volunteer to do it.
Right now, IT DOES! Audacious 3.2 supports the Sound Menu.
I contacted the developers on IRC in 2010, I reported the bug on Launchpad and upstream.
Finally, today's Git version features a basic MPRIS 2 plugin enabled by default that works with the Ubuntu Sound Menu: http://redmine.audacious-media-player.org/issues/14#note-7
Solution 3:
After looking around for a bit, I couldn't find any plugins for that functionality.
However, the sound indicator does let you change Audacious' volume! :D (not that exciting I know).
I would recommend getting in contact with the developers of Audacious and encouraging them to make it utilize the sound menu in Ubuntu.
http://audacious-media-player.org/developers
It's only a matter of time 'till it happens! :)
Solution 4:
I started writing the plugin.
https://bugs.launchpad.net/ubuntu/+source/audacious-plugins/+bug/658001
It correctly registers Audacious in the sound menu but the playback control buttons still don't have any effect.