Lowboy, the bladder is like a reservoir, it hold air and helps with the lower notes that require more air than the higher notes. The Hohner Basso (bass Melodica) also has this bladder. My basso had a pin hole and leaked bad. I put a thin layer of latex caulk (not silicone) over the hole and it did the job nicely. Soon after a new hole appeared, just an old melodica. :(. By the way I will be posting a new video soon where the basso is sort of featured. If you have played a bass melodica you already know that it is not an easy melodica to play.