The resonance of a didgeridoo is another way of describing how strongly the instrument responds to being played, in particular, how intensely and for how long.
A strongly resonant didgeridoo plays more loudly, given the same effort and energy input contributed by the player, compared to a weakly resonant didgeridoo. The sound of a didgeridoo also carries longer on a strongly resonant didgeridoo.
Resonance is a product of the material the didgeridoo is made from and a bunch of other variables related to the construction of the instrument - wall thickness and shape of the bore especially. A key criterion in choosing a good didgeridoo is its resonance.
Here it is important to point out the difference between the resonance of a "tourist" or souvenir didgeridoo and an artisan-crafted didgeridoo. Most souvenir didgeridoos are not made to be musical instruments and may sound flat or muffled. In contrast, didgeridoos crafted by artists who take time and care in the creation of each individual piece are intended to be played and are optimised for performance.
Backpressure can be described in different ways and is an important variable when choosing a didgeridoo. It is the feeling you get when you play into the didgeridoo, the pressure that pushes back at you when you play.
In physics, you might have heard of Newton's Third Law: for every action, there is an equal and opposite reaction. This is backpressure at its simplest. Or another way to think of it is how long will one gulp of air last on a didgeridoo.
An instrument with high backpressure is easy to play and a breath of air lasts a long time. A badly constructed didgeridoo or a lower keyed will have a low backpressure. This means it will be difficult to play and more difficult for you to maintain circular breathing.
Whilst high backpressure is fine for getting a drone and learning circular breathing, accomplished didgeridoo players prefer a moderate-high backpressure, the sort that allows easy circular breathing and does not constrict the acoustics of the instrument excessively.
Responsiveness or sensitivity is merely how well energy transfers from your lips to the didgeridoo. A good didgeridoo is responsive or sensitive to the slightest breath or lip movement and the harder you blow, the louder and more powerful the instrument. A poor didgeridoo, in contrast, feels dead, for example, if the bore is blocked, if there are cracks, or if the construction of the instrument is otherwise not ideal.
The fundamental note of the didgeridoo is the drone note. The plain basic sound of the didgeridoo without any vocals, toots or other sound effects.
The overtone note or the horn is the trumpet like toot that is often used to break up the regular drone of the didgeridoo and to emphasise a particular part of the rhythm. It is played using higher lip tension and stronger air pressure within the oral cavity. Air is forced through very tight pursed lips to produce the characteristic sound.
The horn sound can be made as short sharp sounds or as one long continuous sound. Accomplished contemporary players can play the 1st, 2nd and even the 3rd overtone note of a didgeridoo.
The acoustics of a didgeridoo is the overall voice or sound of the didgeridoo. It is different to the key or pitch in that the acoustics describe not just the fundamental note of the didgeridoo but all its subtle sounds or sub-harmonics.
It is the entire spectrum of frequencies that the didgeridoo produces when playing just the fundamental note. A didgeridoo can be described as having full-bodied acoustics meaning that the frequencies that the instrument produces is spread across the spectrum rather than bunched up in a certain region. Another way of saying that a didgeridoo has full-bodied acoustics is that its acoustics are balanced. In contrast, a flat-sounding didgeridoo has dominant frequencies either in the high or low end of the frequency spectrum.
A didgeridoo can also produce vocal sounds using the vocal cords while vibrating your lips and droning as normal. These can be high-pitched vocal sounds such as bird calls, dingo yelps or other animal sounds or your vocalising can be in any form, such as speaking, singing or yelling
Passive vocal effects are where the player allows his or her vocal cords to gently vibrate or interact with the drone note of the instrument resulting in low humming sounds that are deeper than the fundamental note of the didgeridoo.
Most of the sounds produced by a good didgeridoo player are done with the tongue. The manner in which the tongue moves - slow or fast and whether or not it hits any part of the mouth determines what sort of tonguing effect results.
Tonguing allows didgeridoo rhythms to become more percussive and rhythmic with the introduction of strong accentuated stops and starts and staccato-like beats.
Traditional Aboriginal players from Arnhem Land are renowned for their rapid staccato-like tonguings which can be used to produce complex rhythms.
Pulses are short, sharp bursts of air from the lungs that are forced through the vibrating lips to create a quick loud pulse over the top of the basic drone. Because they are loud, sudden and powerful, pulses are a good way to emphasize the beat in didgeridoo playing and help provide underlying structure to the rhythm.