(See below for: Plans to convert this didge into a didgibone!)
Here is the type of PVC reducer I nest together for a mouthpiece:
After reading up on the acoustics of didgeridoos, I thought I would try to make something more conical in shape, since conical didges are supposed to sound better and have more harmonics.
The easiest way to do this was to combine three different diameters of pipe. I didn't expect this to be much of an improvement over the straight cylindrical didge, but was quite surprised how much better and LOUDER this one sounded. Also, vocalizations came through much better.
Here is a spectrum analysis of a straight didge (top) compared to this one:
This shows (see below for an explanation) the richer harmonics of the didge made with three different diameters of pipes.
These spectrums are produced by the TUNE!IT instrument tuner for the computer, which can be downloaded at: TUNE!IT
Here's a sound sample of various effects on my sectional ABS didge made from three different diameter pipe:
Pseudo-Conical ABS in D
The top spectrum displayed above is the straight, cylindrical didge, and the spectrum below it is the one made from different diameter pipe.
The vertical axis is BOTH time and loudness while the horizontal axis is the pitch of the note, going from low on the left to high on the right. Every few seconds you get a red read out line that runs from left to right and shows what sounds are coming through at that time. The height of the bump or mountain indicates the relative strength or volume of the sound.
The large mountains to the left are the basic drone, which is loud, low and almost constant. Moving to the right, you see what harmonics are also sounding. These harmonics enrich the tone of the didge and also can be selectively emphasized by altering the position of the tongue and lips. Check out my F Didge Sound Sample to hear the emphasized harmonics.
Note that for the cylindrical didge you can get the drone in D, but the next two D harmonics are weak. The conical didge, on the other hand, gives you strong D's for the next two octaves.
Converting the sectional didge into a tuneable didgibone
Here is an easy way to convert an ABS sectional didge (such as the one above) into a tuneable didgibone. This involves removing the seating rim inside an ABS connector, so that the smaller pipe is free to slide in and out:
In the above diagram, section 3 becomes the sliding pipe. If you cut section 3 to a length of 22 inches then you have a sliding didge that goes from the key of C up to the key of F.
At the moment I am leaving the slide section with a very tight fit, so that it doesn't shift around once it is the length you want. For slide didge effects it would be necessary to sand down the inside of the connector further so that section 3 can slide more freely. I haven't done that yet because I am mainly interested in having a didge that can quicky change key, and that stays in place when the required key is found.
Once you have established the key lengths I expect that you can etch a marker onto the outside of the pipe.
My sectional didge in D toots an F. An interesting advantage of the sectional didgibone is that when you increase the length of the sliding pipe to 31 inches you can set the key to D and find yourself tooting in D as well. This is the first ABS didge I've ever made that can actually toot the same key note (an octave up), at least for the key of D. The second toot is an F# which also falls happily into the key of D. I have tried for a long time to get an ABS didge that toots the same note (an octave up) as the basic drone.