[LAU] Xfce, jack, and GStreamer

[Don Strayer]

I'm running Debian Sid and have just installed Xfce. I'm having trouble
getting Xfce's audible alerts to work. As far as I can see, they're the
only sounds on the system that want to go through GStreamer.

Sound is through jackd2 and FFADO to a Saffire PRO 24. Jack is set up as
described in
http://alsa.opensrc.org/Jack_and_Loopback_device_as_Alsa-to-Jack_bridge

(That website is currently unavailable. It would sure be nice to have
another copy of that page for reference. A copy of the .asoundrc is
here: http://pastebin.com/1WLtqeJ1 )

Programs that speak directly to jack work. Sound in Flash videos such as
Youtube works. "speaker-test -c2" works.

"gconftool-2 -R /system/gstreamer/0.10/default" shows:
  chataudiosink = jackaudiosink buffer-time=2000000
  audiosink = jackaudiosink buffer-time=2000000
  videosrc = v4l2src
  visualization = goom
  audiosink_description = Default
  musicaudiosink = jackaudiosink buffer-time=2000000
  chataudiosink_description = Default
  audiosrc_description = Default
  audiosrc = jackaudiosrc
  musicaudiosink_description = Default

"gst-launch audiotestsrc ! audioconvert ! audioresample ! jackaudiosink"
produces a tone in the left speaker.

So does
"gst-launch audiotestsrc ! audioconvert ! audioresample ! autoaudiosink"

When I run xfce4-mixer, I get an error message:
"GStreamer was unable to detect any sound devices. Some sound system
specific GStreamer packages may be missing. It may also be a permissions
problem."

When I try to get an audible alert from, for example, the Orage calendar
program, there is just silence.

What am I missing? Or am I barking up the wrong tree?