How to use Pangea songs?

[calmon]

Actuarian said:
I really wanted to see how the spell worked, so I attacked a province with no archers(I also had no archers), and set my troops to guard commander. The AI still overrode the script and kept casting shards.

Like i wrote i tried the same and to me it works fine. Do you fight special opponents like undead? Try normal independents even with archers.