Comment 7 for bug 1396986

I, too, believe that Ubuntu phone's sound GUI is ill-designed. It does not give the user control over what channel's volume she changes. Instead, the OS tries to be overly clever, such as always controlling the app in foreground (which may or may not be desired), adding some bias when speakers are on in the phone app (resulting in sound being played though volume is zero and the crossed out speaker symbol isshown), games starting with sound on even when silent mode is on, etc, etc.
See also
Bug #1483890
Bug #1384274