When Chris purges Nehushtan and dons Ichii-bal during her fight against Hibiki in episode 7 of the first season, she complains about how she has to start singing now. And indeed, Ichii-bal, like Ame-no-Habakiri and Gungnir, generally requires the wielder to sing while transformed (because of, like, phonic gain, or something?).
However, neither Chris nor Finé sing when they wield Nehushtan (thereby depriving us of what would surely have been a glorious Sawashiro Miyuki battle song).
Why is that? Why doesn't Nehushtan require its wielder to sing?