Probably very common but I can play my cheeks (of my face!) with a pair of pencils or the tips of my fingers. You get the different notes by opening and closing you mouth or shanging its internal shape.

At the peak of my powers I could do a good Willian Tell or Bum of the Flightle Bee and could probably still conjure these up if asked politely. This all sounds rather good through a decent microphone such as a Shure SM58 and high power PA system.

Peace

moo