Mal and Ace went on a TARDISy field trip way back when to a whackadoodle planet with crazy purple ladies and blue glowy grapes that Mal is in love with. Much more so than the crazy purple ladies. Ace brings them back for him on occasion.
Well, if no one else is going to answer this one...
Trick #16, or a "nice use" thereof, involves summoning a wind to break the reeds by the riverbank, and then blow across the broken ends, to play music that lulls a target to sleep.
(For the record, as of writing this I haven't seen that scene in a couple of weeks. That's entirely from memory.)
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