That language is so damn neat. "Would you be. If not, it's fine, I just thought. Would you be willing to teach me how to do that? To whistle in Centaurian?" They know a shit-ton of languages already, and learning an actual specific alien language-- especially one somebody here knows but can't share with anyone-- sounds like a worthy addition. And they're pretty sure they can whistle. They whistled for the junkyard dog back in Beacon. Surely it can't be harder training a whistle than training a voice to sing the spirits' language.