Paul White explores the outer limits of physical modelling on a budget that wouldn't even buy you a decent pair of shoestrings!
Digeridoos aren't exactly at the centre of mainstream British rock and dance music, but they do seem to be increasing in popularity, and are turning up in all types of contemporary music from the obvious World and Ethnic genres to pop.
Should you want to incorporate the sound of a digeridoo into your music, the easiest way is to use a sampler. There's no shortage of available digeridoo samples — but it can nevertheless be a problem finding a sample that fits in with your track. For a start, digeridoos are monophonic, single‑pitch instruments, and if you move a sample more than a couple of semitones away from its original pitch, its artifacts start to show. On a typical sample CD, you might find a few example phrases, but the chances are that they'll be in the wrong key, unless you're prepared to write your song around the sample.
A more major problem is that digeridoos tend to be played very rhythmically, and while it is possible to use a basic drone underneath your tracks, it's always better if you can find a rhythm that compliments the rest of your composition. In short, samples are fine if you're prepared to work around what's available, but if you already have a song and you want a digeridoo part that's going to fit perfectly, ready‑made samples are always going to be a compromise. So — what's the alternative?
Physical Modelling
When I first came up with the idea for this article, I thought I'd have a go at creating the sound of a digeridoo by means of physical modelling techniques, using a synth as a sound source, a wah‑wah pedal to add articulation, and a short delay with lots of feedback at the end of the chain to create the tube resonance. By fine‑tuning the delay time, you can tune the pitch of your virtual digeridoo — but sadly, the real problem is that this 'virtual' digeridoo sounds nothing like the real thing! As an avenue for exploring new and interesting sounds, this simple setup is great, and you can get some very useful results — but don't let me or anyone else kid you that it will sound like the real thing. Actually, since then, I've created a patch in an Emu Morpheus that gets a little closer, but the digeridoo is such an overtly organic instrument that any electronic approximation is destined to be pretty rough.
The direction of this article took a radical turn when I picked up a tape in a music shop on how to play the digeridoo. I reckoned that if I could make a simple digeridoo, I could squeeze enough of a note out of it to sample the result before I ran out of breath. Thereafter, I decided to abandon my physical modelling research in favour of building a physical model. The results of my endeavours would never have made it onto these pages if they hadn't been very successful, cheap to implement, and relatively easy to achieve.
Construction
Before you can start learning to play the digeridoo, you obviously need an instrument. This is where my teaching tape came in handy, as it suggested beginners start by using a length of plastic pipe. I've found that 1.25‑inch or 1.5‑inch plumbers' waste pipe works best, and a length of around one metre seems to suit most people. Once the pipe has been cut to length, all you have to do is create a mouthpiece, because the sharp end of the tube can leave your mouth looking as though you've been attacked by a maniac with a pastry cutter. The traditional method is to dip the end of the tube in melted beeswax until you've built up a rim of around an eighth of an inch thick, and although you can experiment with candle wax, you'll find that it softens as you play, and eventually falls off. I found a more permanent solution was to use Rapid Araldite smeared onto the rim of the pipe, and then warmed over the stove to make it runny. Keep rotating the pipe as you warm it, and you should end up with a smooth mouthpiece as shown in Figure 1. Any small bumps can be sanded off after the Araldite has hardened, and the resulting tone you can get out of your plastic digeridoo is easily good enough to record.
I've already mentioned that pitch can be a problem for digeridoos. Ideally, you need a whole set of digeridoos, but I tried to make a tunable version using a length of 1.25‑inch pipe for the mouthpiece end, and then fitting a sliding section made from larger 1.5‑inch pipe, which enables the length to be fine‑tuned. A couple of elastic bands wrapped around the thinner pipe stop the thicker one from falling off — Figure 2 shows the arrangement I used. A further benefit of the sliding system is that when you start, your lips seem to work better at some frequencies than others, so you can adjust the length of the pipe to make your digeridoo easier to play.
Once you have your instrument, the first hurdle is to get a note out of it, and while everyone else, including my seven‑year old daughter, managed to produce something recognisable within a minute or two, all I could get out of the thing was something disturbingly reminiscent of a flatulent goat that had been force‑fed on a diet of sprouts and cider for the previous fortnight! Fortunately, salvation came to dinner, in the form of John Harris (aka the Demo Doctor) and his wife Judy, who, it turned out, had been learning the digeridoo too. After a few pointers (see the 'Circular Breathing' box for more details), I had it cracked, and since then, progress has been rapid.
Playing
Before you begin playing your digeridoo, it helps to do a few face‑stretching exercises, including a minute or two of spluttering and whinnying. This makes you look a real prat, so it's best to do it in a credibility‑proofed environment! If you now transfer your gently spluttering lips to the mouthpiece of your improvised digeridoo, you should find that you get a note. If you're having trouble, try using less air than you might imagine, and also try the mouthpiece to one side or other of centre; most players seem to use the side of their mouth rather than the exact centre. It is important to make sure there's a good seal between the mouthpiece and your mouth at all times.
Once you have the basic drone, you can modulate the tone by moving your cheeks as though you have a mouthful of mouthwash which you're sloshing from side to side. The sound will be instantly familiar, and by pumping your cheeks rhythmically, you should be able to play a bar or two of rhythm before you start to collapse, with stars rapidly invading your darkening field of vision.
Further tonal articulation can be produced by playing a simple drone and then moving your mouth as though you were trying to describe the filter section of the latest analogue synth to someone — with just a little practice, you can get quite a neat filter sweep sound going! Other traditional Aborigine techniques include doing animal and bird impressions while droning, and even speaking words as they play. Most of these techniques can be explored in a rudimentary way without too much effort, but just to make sure I stay on the right side of those who can play the digeridoo properly (I don't want another stream of abuse like the one I got from the bagpipe proponents a few months back!), I ought to make it clear that there is more to serious digeridoo playing than this. Before moving on, I must warn you that learning to play the digeridoo is pretty antisocial — it's not the noise that upsets people, but the spit dribbling out of the end of the tube and the slime running down your chin. Perhaps that's why the Aborigines seem to play mainly at night...
Recording
The digeridoo is at its best in a live environment, and will sound most impressive if you can arrange it so that the tone produced is reflected back at you. If you don't have a live room to record in, try playing facing a window or hard wall. Set up a mic a couple of feet in front of the instrument, pointing towards the open end of the pipe, and experiment by moving the mic slightly to one side or the other to see how the tone is affected. Once the levels are set, try turning on your recorder and just playing a series of drones and rhythmic phrases to see what you come up with. After a few minutes, you should have something worth sampling, though if you are working on a specific song, get the backing track up on headphones and jam along to see what you can come up with.
Once you've got something worth sampling, transfer it into your sampler and try to find a loop point that leaves you with a whole bar, or two‑bar section. If you're playing rhythmically by pumping your cheeks, you can usually loop 'on the beats' to avoid obvious seams, but if you need to resort to crossfade looping, that should still work OK. On long, non‑rhythmic drones, crossfade looping is very helpful, but still try to keep the looped section as long as possible, so that you can capture the movement of timbre that characterises the digeridoo.
To enhance the sound once you've sampled it, try adding a bright reverb, and maybe a subtle echo delay. You can boost upper mid frequencies with EQ to bring out the raspiness of the tone if you need something that cuts through your mix, but avoid over‑equalising as you would with any other natural instrument. Who knows, you might get more interested in the digeridoo as an instrument, in which case I'd strongly recommend you buy a tutorial tape. The one I have is called Digeridoo — How To Play, and it's by Alistair Black.
The Digeridoo
A traditional digeridoo is generally made from either a hollow branch or from giant bamboo. I've seen commercial models made by cutting a branch in half, carving out the inside, and then gluing it back together — which is is probably quicker than the traditional way of waiting for termites to do the job for you — but for learning purposes, the plastic waste pipe version described in the text plays well, and sounds surprisingly good. The size of pipe you use will depend upon the size and shape of your mouth. The larger bore pipe produces a deeper tone, but for me, the narrower pipe is easier to play, and has a brighter, more interesting timbre.
As well as being a fine‑sounding instrument, the digeridoo is considered to be very therapeutic, so if you're one of those people who likes to smoke lentils and go 'Om' quite a lot, this is definitely the instrument for you.
Circular Breathing (And How To Cheat)
Most people can, with very simple instructions, get quite impressive and authentic sounds out of a digeridoo — what takes the real practice is learning the circular breathing that keeps the thing going. Fortunately, technology can help here, because if you're going to sample the result, looping takes the place of circular breathing. All you have to do is play long enough to complete the drone or rhythmic phrase you need. With one breath, you shouldn't have much trouble getting a 20‑second drone going, and most sampled phrases need only be a couple of bars long.
One myth that needs to be dispelled is that circular breathing means breathing in and out at the same time. What really happens is that you use your cheeks as bellows to squeeze out air at the same time as you snatch a quick breath through your nose. The trick is to keep the lips vibrating as you do this, but like most things, you practice and suddenly, when you're about to concede that it's quite impossible, something clicks and you can do it. While it can take less than an hour of practise to get recordable sounds out of a digeridoo, it took me probably three or four hours, spread over the period of a week or so, to get the circular breathing right. When you finally get it, the joy is every bit as great as when you learned to play your first F major chord on the guitar without fret buzz.
Because the tone changes when you switch from releasing air to drawing it in, your breathing should be synchronised with the rhythm of what you're playing, and though you'll invariably find yourself with either too much or too little air in your lungs after playing for a minute or so, a few more days of practice will smooth this out.