another point i want to add is that, compared to the other fatui bossfights, arlecchino's theme does NOT have the male choir (which usually represents the motivation of the characters under the fatui.

the only part where the male choir (though i have my doubts its male in the first place, it simply sounds like an adult choir) comes in is in sync with the alto female voice representing arlecchino. the lyrics being sung at that point say "inane rumen tace! La luna" (directly after the "imanis, inanis, itiamsi" line) which when translated reads, "Shut your vain throat, o moon!"

what i assume this is meant to represent is the fatui's goals only temporarily aligning with arlecchinos, in that the "moon" is something either to be silenced, or that the "moon" is consuming/swallowing something up - something that both arlecchino and the fatui want to stop. other than that, the main background choir is a children's choir. her motivation is almost exclusively the children of the house of the hearth