If gibbons are high on helium they sing like sopranos. Scientists in Japan, (of course), did an experiment in which they stuck a bunch of the melodious monkeys in a room that's air had 50% helium. Gibbons have similar vocal folds as we humans and can "sing". I'm not sure what part the helium had to play in it if the monkeys can make the noises on their own. My guess is that the scientists just thought it would be hilarious. It's a fact of the universe that nothing is funnier than monkeys. Also, which one of us has not sucked helium from a balloon and laughed like a demented imp. Put them together and it should be comedy gold...only...I think I'll be hearing this noise in my nightmares tonight.