Great stuff! Will definately try that out soon!
Maybe it could be handy for that to use the "multiple-application-feature" of the PXML/PNDs?
So there could be only one PND, but different ways to invoke timidity. I'm using this eg. in my Links2-PND.
I'm not that deep into timidity++, but what does it say if you just call "timidity -h"?
Can you see the ALSA-Interface listed?
This is from my Debian Squeeze desktop-machine:
Available interfaces (-i, --interface option):
-in ncurses interface
-ie Emacs interface...
At Wikipedia is a good explanation of the Loop-Device.
Unmounting is as simple as "umount /mounted/path", but you first have to close all references to it.
With "lsof /mounted/path" you can see what processes are still referring to it.
Change it with Settings -> Preferred Applications -> Web Browser to read (note the single quotes):
'pnd_run /media/YOUR_SD_CARD/path/to/links.pnd' "%s"
This works for me eg. when you click on the Browser-Icon on the Xfce-Panel.
But this has really a caveat: if some application now tries to...