There's a guy here in Sydney called Mick Griffin who makes tunable didges by putting a piece of PVC pipe inside another slightly larger piece and sliding it up and down like a trombone. Personally, I like to play my tummy with my fingers - it makes a very satisfying slapping sound, rather like hitting two fish together. It's also quite close to the bowel, and there might be some variation in sound, depending on how much I have eaten (or drunk).You can add beer or wine, or Jameson's for pitch variety, too. Organ recitals are another matter entirely.