Didgeridoo making is not as simple as you might think. You need to know some basics in physics to ease the process of fabricating a playable didgeridoo. OK, look at the process of building a simple PVC didgeridoo, just cut a piece of PVC tube, smooth the edges and that's it. No, it's not that simple, a playable didgeridoo is an instrument which is blown with a certain musical key and this is what music is all about. Bear in mind that didgeridoo making is not a just cut and paint process.
To make a didgeridoo from hollow materials such as PVC or plastic tube, the most important thing to consider is the length of the tube to be cut. A certain length of the tube will produce a specific musical key. It is easy to calculate the length of the tube to produce a musical key because the tube has an even thickness throughout the length of the tube. In my reading, there are some discussions on choosing a preferable size of the tube (inside diameter) for making a PVC didgeridoo. I could understand that it is not really a matter how big or how small is the tube, the length is the main concern. The explanation is, the width or the size will not affect the musical key but it just amplifying the sound produced when blowing through the tube. The theory does not apply to the genuine didgeridoos produced by the Australian Aborigines where the didgeridoo possesses an irregular inside diameter because it has been naturally hollowed by termites. This makes the original termite-eaten didgeridoo so unique and produces very interesting sound characteristics.
Well, I am not an expert on physics and I may not be able to elaborate much on this subject. I would suggest you to visit any site on the net that explains in details about didgeridoo physics. As in my case, I tuned the newly made didgeridoo by using a tuner which is available in any music stores. I welcome any comments on this subject, especially from Mr. Rob, Australia.