This will seem really random and I don't have the foggest clue how he did it, but my uncle made a digeridoo out of PVC pipe. The band members here in Avon do breathing exercises with 1" ball valves (PVC) to increase their lung capacity. They start with the value mostly open and force air through it. As the training continues they make the opening smaller and smaller which requires more force to move the air.This was a low cost alternative to existing tools for horn players (ie to increase lung capacity). These might be possible alternatives if the digeridoo is out of her budget.