I read in a book the other day that inhaling helium would raise the pitch of a clarinet. Well, this just needed to be tried! I took a balloon from work and brought it to school. After school I went into the band room and a crowd gathered around. I set up my clarinet and readied the balloon. I got a baseline pitch on my clarinet, I was in tune. The consensus among the group was either that the helium would do nothing or that it may raise the pitch a couple of cents.
I cut the end of the Mylar balloon and inhaled deeply. I then played a concert Bb. At first, no change, but then to our amazement the pitch glissed up at least an octave! Cue uproar of laughter! It was the funniest thing ever, nobody expected it! The helium TOTALLY effects the pitch of a clarinet! We did it again with the same results and more laughter. The notes starts normal, but then smears up an octave! Amazing. If you have a clarinet and can get helium, do this experiment, it is absolutely a blast.