Comment # 4 on bug 904043 from Guido Berh�rster

The default mixer for Xfce has been xfce4-mixer since before the 12.3 release,
but it doesn't really matter since any mixer based on gstreamer like
xfce4-mixer or gmixer will not work well if you install pulseaudio because the
gstreamer pulseaudio backend is totally broken.

Unfortunately the is no chance to get this fixed since the gstreamer developers
have removed the mixer interface altogether in newer gstreamer versions, so I'm
closing this. If you need pulseaudio you'll have to use another
pulseaudio-based mixer, e.g. pavucontrol or mate-volume-control.