Adjusting volume with GUI app for USB audio?

[Jesse Sheidlower]

After assorted work, I've gotten USB audio to work on my
computers (FreeBSD 6.0 and 5.4); I select the USB speakers
with "sysctl hw.snd.unit="1"" to get the pcm1 device.

I find that _some_ graphical volume-control utilities don't
work with the USB speakers. These include the GNOME
volume-control applet, the volume slider in xmms, and the
GNOME volume control application (not the applet). However,
some _do_ work, including the volume control in gmplayer and
the volume control in Rhythmbox. Furthermore, the commandline
mixer(8) works fine--with the speakers plugged in and
selected, "mixer" reports on bass, treble, and speaker volume,
and I can adjust the volume with "mixer speaker 60" or
whatever.

However (again), adjusting the output source in those apps that
allow it has no effect--in the GNOME volume-control applet, for
example, I only have the device choice of "OSS Mixer", and 
whether I select "Volume", "PCM", "Speaker", or anything else,
this just won't control the speaker volume.

Any suggestions? It's not the end of the world to use mixer(8)
but it's often inconvenient.

Thanks.

Jesse Sheidlower