How to turn HDMI video off but keep audio on (slightly OT?)

[Aryeh Friedman]

I have system audio  playing through my HDMI connector under XFCE 4 and
have the power management set so that the monitor/host turn the monitor off
(both audio and video) but when I am listening to music and doing other
things around the house I want to make it so the video goes into power save
but not the audio (very annoying for it to cut off in the middle of song
and then have to run over to my desk and waggle the mouse to force the
power save mode off just to get audio).

Any ideas on how to do this?

-- 
Aryeh M. Friedman, Lead Developer, http://www.PetiteCloud.org