Yes I recently saw an historic instrument demo at Oxburgh Hall by a multiinstrumentalist dressed like sir walter raleigh. The bladder pipe is an oboe style double reed attached to said bladder attached to a wooden tube wi' holes drilled in with a red hot poker. Sheeps horn on the far end optional.The bladder acts as a reservoir of air, so you can get a continuous stream of air without learning circular breathing. Sounded like: a musical squealing pig. Pretty cool. And a whifft of pork scratchings with every tune. Bladder needs to be untanned, he implied.