I have what I think is a simple question for which I have searched and searched for an answer but obviously unsuccessfully.
I am using KDE4 in Mint 14 and I want routine system notifications (and start-up sounds, etc.) to be sent to my small USB speakers, while directing higher quality stuff, so music, through the line out (or front headphone jack) of my system. So through Kmix [in the bottom panel] -> Audio Setup I can get to the Phonon KDE Control Module, and my two main sound outputs are there, test fine, etc. (although for some reason only the left speaker of the USB speakers work, but that's a different problem that I haven't resolved yet) and I can change the device preference orders. What I am puzzled by is how the categories are actually determined. So I assume there is some database file somewhere on the computer that defines, for example, 'audacious' as "Music", but why, when I select my USB speakers for first priority in "Audio Playback" for everything (except 'Music'), do for example Thunderbird email notifications get classified as 'Music' (along with the log-in and log-out and similar system sounds) and so sound gets directed to headphone and line out jacks whereas when I play YouTube or web browser-embedded videos of news, for example, the sound does go to the USB speakers (unfortunately in mono at the moment)?
Somewhere there must be a listing (and I would hope customizable) that states that such-and-such an app (for Phonon control purposes) fits in a specific category.
I do also go to "pavucontrol" ('Pulse Audio Volume Control' in the KDE 'Sound and Video' menu) which affects the actual devices, but it has no affect on device preferences as set up in the Pnonon KDE Control Module.