I don't get that tune, from what I understand of the guilds background a true
animist is a ghost liberator, a templar never gains access to that skill and
monks are rare. The liberator also due to the way he is always in conntact with
the souls of the dead and fights along them has a rather strained relationship
with the sisters of las.
Now why should soul chorus, depend on the help of a nun? Since soul chorus got
tuned I didn't used it a single time, simply because getting candles is far to
much to bother for a 3min effect, even if it helps the complete party (not that
an liberator animist spends much time in partys).
So if you really think that the spell requires another ingredient how about
making it something you can actually get without falling totally out of roll?
How about making it something gathered in the spiritworld?