Make, Play and have fun
Changing the sound of your your plastic didgeridoo
As with a wooden didgeridoo, the internal size and shape of the bore directly and distinctly affects the sound.
The bores of termite hollowed instruments are irregular and even split didges where the bore is worked by hand, the bore will still be irregular, which is the opposite of plastic didges.
This is both good and bad - the sound that is reproduced is constant and regular, and the key of a given length of pipe will also be constant, whereas conversely this makes the instrument sound like a plastic tube and does not have the character and individuality of wooden made instruments. Adding to the bore adds weight to the instrument making it feel more substantial.
Therefore by jazzing up the inside of the bore and altering its dimensions will help to give some uniqueness to the sound. It's possible as well to change the backpressure which again, will change the performance of the instrument.
I use PVA wood glue and sawdust to create this.
Before doing anything else, the bore must have a key for the glue to grab to otherwise it can have a tendency to chip and peel off. As mentioned earlier in these pages, I use a long piece of dowel with sandpaper attached to the end. I normally staple the sandpaper to attach it because then there won't be anything sticking out of the dowel that may catch and scratch surfaces unnecessarily.
Give it a good bit of elbow grease and really score into the surface. This in itself will change the sound of the instrument as the sound waves will not travel as smoothly down the bore.
Once scratched up the fun begins. I will invariably pour a layer of neat PVA down the bore and let it run down the inside, rotating the pipe to ensure thorough coverage. If the layer of glue is not to thick it won't take to long to dry and will provide a good surface for anything else chucked down the bore to adhere to.
Needless to say, the benchmark here is to play the didgeridoo after every stage and process, stopping once you have achieved the desired sound.
Once dry, I will then add further layers of glue until I am happy with the results. Depending on what I am trying to achieve, I will add sawdust (or sand) to the glue as will add some body to the glue and if mixed in a good ratio, will help the glue set quicker. It is best to add several thin layers rather than trying to get it all done in one go. You can do it in one go but you will end up waiting ages for the glue to dry enough to stop dripping down and out of the bore.
Using another piece of dowel (or the same dowel with the sandpaper attached but round the other way) poked up the bore will help to spread the glue around to make sure you get it all covered.
One other technique you can use is once the glue starts to go off and retain some of its surface tension - it doesn't so much run, as sag - block off the mouthpiece end and stand the didgeridoo upside down. As the glue sags back down towards the mouthpiece it will get narrower as the glue accumulates at the blocked of end. Get it right (don't try and over do it) and the result will be a tapered bore which changes the backpressure and pitch a lot.
To me this process more than any other makes a plastic didge sound more natural and realistic, adding a distinct uniqueness to every piece of plastic regardless of the outside shape.