I assume you have the JP version of PSU:AotI (if not, you can dl it
here).
For music files, I've made
this. Save this *.txt file into your DATA folder (\SEGA\PHANTASY STAR UNIVERSE Illuminus\DATA\), rename it to suppress the *.txt extension (and change it with the *.bat one) and then run it.
If you only want to get some music files, just use the list to localize the wanted files.
Some of the SE files and the dubbing is contained into the 010169910af0dfc0572829c94431f24d file, which can be opened thanks to the Essen's tools.
All of these *.adx files can be played with
Foobar and the
vgmstream decoder. And with
LAME, you can convert the *.adx in a more common format, like the *.mp3.