Didgeridoo (Yidaki)

David Beale

Philosophy and physics for musical instruments as resonant systems

My didge has a variable-length insert tube.  With any didge I can play a continuously ascending or descending note, and sets of discrete notes in scales including quarter notes. On this didge I can play any frequency with a range of a bit more than two octaves, without variations to its length: That's the opposite of what is usually expected to happen. Here I'm saying how you can play some wind instruments with continuous pitch variation even if they are a fixed-length pipe. For example, the human voice can vary in pitch (frequency) continuously, keeping the tone the same and without varying any pipe lengths.

The background track was made for the Barwang video, below.

See also a page with instructions for learning to play the yidaki

The background track involves a technique, more complex and subtle than overblowing, to produce different notes from a didge. It shows tight control of what may be called "co-resonance"; the technique is extra to the standard concepts and sensations related to embouchure for non-reed wind instruments (it works for trumpet, Tibetan horn...). This extra is similar to embouchure, with extra complexity for producing continuous pitch variations.

The background track was played on a length of plastic water-pipe; it was the first recording I did using the say "dominant co-resonance" method for variations in the pitch of a fixed-length pipe. Other videos here are of me playing a wonderful didge made by Dr Didge Dolphin. This new didge has length variability by sliding an insert pipe, like a trombone; the facility allows perfect tuning with other instruments while retaining optimized tonal qualities; however the sliding insert is not used, in these videos, to produce the wide range of frequencies. The videos are of me doing drills not making music...

Didgeridoos have potential each for a continuous range of at least two octaves. The techniques I use are additional to overblowing to get many notes, and in-betweens, from a fixed-length instrument. The length-dependent method, for variable pitch, is here: http://www.phys.unsw.edu.au/jw/flutes.v.clarinets.html. The UNSW article shows a complex tune being played on an ancient-style fixed-length trumpet. To produce continuous notes, rather than notes mathematically related to the length, needs the new modification/addition to the technique demonstrated in the article. The article presumes that a fixed-length pipe can only produce resonances related to that length; but I've proven that embouchure control can produce a dominant resonance in co-operation with the pipe.

"Co-resonance" is a way to describe the relationship between, for example, the strings and body of a violin. The strings on their own would transduce most of the sound energy into heating the air, randomly; whereas a violin's added projection-surfaces project the sound vibrations systematically into into the air. The strings' tension-variations sendempowering energy into the body of the violin; the strings, controlled by the person, direct the more powerfully sounding and more complex resonances within the body of the violin. Similar feedback-control enables singers to produce the sounds they do.

The techniques I'm using are almost identical to singing/speaking techniques; so a controlled resonance, into a length of external pipe, produces continuous pitch variations; additional to discrete stepped resonant-frequency changes. Observe the practice-drill videos here: they include examples where, after an arbitrary resonance is established (without being related to pipe-length) subsequent notes do follow mathematically from the first resonance; indicating co-resonance between the embouchure and the pipe's own slight tendencies to resonate.

Wind instruments, of fixed lengths, can vary their pitch as much as musicians care to believe they can. Systems interact when their resonances are complementary. The system supplying the energy can have control; as with a singer or speaker producing a wide range of notes all sounding the same other than their fundamental frequencies of vibration. Musicians who play didgeridoos tend to believe that the didgeridoo has control; so they learn to supply energy strictly in compliance with the didge's dominant frequency. When the length of the pipe is allowed to be in control, then the primary resonance is mathematically strictly related to length. Wind instruments are mostly played with embouchure allowing the didge, for example, to play only one note plus a few higher-note toots. Some musicians can produce a note one octave below the nominal key-note of the didge; but this new technique can produce continuous notes an octave above and an octave below the nominal "key" (only) note. [Producing more than + & -one octave is proving to be difficult but possible. Doing this involves me going red in the face, etc., straining...However, like whistling and singing, monitoring one's sensations does extend the range of frequencies more than 4:1]

In electronics terminology, the amount of energy needed to be put into a resonant system, to maintain resonance, gets compared with the amount of energy circulating (say as "standing waves") The ratio is called "Q"; it regards the "quality of the resonance". Resonances in musical instruments have their equivalent of electronic's "Q". Playing a didge with variable frequency relies on extremely hi Q; the notes still last for a very short time, only enough to ensure normal breathing can be done while pushing the air out through the mouth. The input energy is extremely low for this new method; similar to producing a loud ring from a wine-glass or Tibetan Bowl. The strings of a piano sound for much longer than resonances in a didgeridoo; because the energy put into a didge is tiny — mostly from the tongue and mouth, cheeks — compared with a piano's relatively high-energy movements applied to strings and the body of the piano. The energy put into a piano mechanism is hugely more than the extremely low-energy embouchure-related resonances of loud sounds from a didgeridoo.

http://www.phys.unsw.edu.au/jw/brassacoustics.html has articles related to fixed-length pipes producing variable pitch; but the notes are shown to be mathematically related to the length of the pipe; whereas my technique relates pitch to a resonant system that is dominant over the pipe-length. I add the idea of "co-resonance" because I observe how mouth-plus-everything-else can control resonances using shapes and tensions additional to the lips.

Some play the didge believing that their lip vibrations are fitting in with the didge's fixed-length non-variable pitch. Their beliefs prevent any attempt to play tunes on a didge!

Interactive resonances are more complex than simple two-element resonances as for example a reed and a tube working together.  The UNSW article says this: "Paul Plunkett, professor of trumpet at the Conservatorium of Winterthur, playing the Prince of Denmark March on a baroque trumpet in D, whose harmonic series we see here, followed by the first two bars of the march..." The page has the actual sounds in mp3 and wav format, with the score, followed by "All done with the lips: there are no valves on a baroque trumpet. (This instrument plays in the baroque tuning of A = 415 Hz, so the pedal note or fundamental is, in modern tuning, Db below the bass clef, so the series is nearly an octave lower than that of the C trumpet discussed above".  The presumption, "...done with the lips..." is worded as if the statement is a misunderstanding of resonance and embouchure.

The didge can be played like the above Prince of Denmark March. The demonstration has many notes close together without changing the length. The didge, and many other musical instruments, can also make sliding-continuous frequency variations. This nebulous nature of resonance is another basis for some instruments being difficult to tune. 

All musical instruments may be regarded as Alive. Every part of the instrument, including the musician, is a member of it's own orchestra, in harmony, with every part of the being having importance. This idea gets away from the idea that a didgeridoo is played by  "blowing raspberries" or getting the "lips" to vibrate (ok that's the first impressions --- sorry no offense intended). The didge can play more than one note related to the length of the didge. The whole mouth and to a slight extent the chest and diaphragm...everything to do with singing and playing any musical instrument...are all cooperative towards producing communications as directed. The spirit of the person works the human body creatively. Actual vocalizing can be added to complex didge techniques; the same as the sounds are added to ordinary didge playing; although I could only add vocals when producing didge sounds using the conventional technique I originally learned.

The technique I use includes: (i) Overblowing (re also Paul Plunkett's skill above). (ii) Embouchure-related dominance of co-resonance with the didge. (iii) "Catastrophe" theory re stability in resonant systems being switchable between stable systems in non-linear jumps triggered externally by overstressing relevant variables. For iii the principle can be applied by playing discrete notes that are unrelated mathematically to a musical scale key of a preceding note; and after a new resonance is established, then subsequent less-dominant resonances (notes) relate mathematically to the first dominantly-chosen frequency.  Control of the resonance is delicate; it is biased in favour of the natural length-related notes of the pipe. When the embouchure control is delicate enough, then, relatively, after a resonant frequency is established then the subsequent frequencies will follow mathematically-related natural intervals; until/unless the resonant system is forced into a new temporarily-stable balance (between all the variables).

An example of "catastrophe theory" is a garden hose with the ability to change the output from a spray to a rod shape: Although the adjustment is a continuous screw-thread, the adjustment has to be exaggerated a lot to force the output to jump from spray to solid. Try this yourself; it's quite surprising! Changing from solid to spray is similar: The hose end has almost zero mechanical slop in its mechanism; yet the hose end has to be rotated far into the opposite direction, to produce the change from spray to solid, and visa-versa — two stable situations that need a large change to jump into an equally stable set of variables, in defiance of the static formulas for both of the stable systems.

Wind instruments can vary pitch continuously by strong dominant resonance, to avoid "catastrophe theory" that would slip the key into an alternative stable dominant co-resonance. If control is relaxed then, after producing a new note that is not mathematically related to the previous note, then the following notes relate mathematically to the presiding key.

A variable length didge helps tune to other instruments. Fixed-length didges can make quarter-notes, half-notes and arpeggios...accurately, using the technique in the above URL re UNSW. I've noticed, when changing notes, that any note once started tends to set the pitch of subsequent notes. Forcing the pipe to resonate at an off-key frequency can reset subsequent notes — so any series can be easy to keep in tune (it can be forced to be out-of-tune with any previous set of notes). Such resonance-locking should be able to produce hypnotic/meditative binaural beat frequencies when two or more didges and other instruments are in the same area but not close enough to lock into each other's key changes.

Absolute continuous control, of the output of a didge, enables the didge to tune naturally into any surrounding natural frequency tendencies. Spiritually, this follows the principle that frequencies in any dimensions may be in harmony and gather energy, by resonance, with frequencies in different dimensions. Resonating with the surrounding shapes of the land, and the unseen realities in other dimensions, can happen when a musician plays any instrument according to the say "laws" of Nature additional to the "laws" of physics.

Tracks here show exercises with resonance additional to lip frequency changes. The background sound track is by a 3m (10') length of  42.5mm plastic drain-pipe with a size-adapter for the lips. It was played in one non-stop take for a YouTube video. http://messagestone.net/Videos/index.html#Message-Stone_at_Barwang .

A magnificent didge by Dr. Didge Dolphin is used for the videos other than the Barwang video track (background to this page). Julian Silburn http://rajaju.com http://soundalchemy.com.au taught me the conventional way to play a didge; he also recommended the Dr. Didge Dolphin didge for me.

Didgeridoos and all musical instruments can resonate spiritually with energy as real as present physics/science/engineering knowledge relates to light, movement and matter. Playing musical instruments can focus intent/prayer/faith and they may resonate with loving energy from Earth. The player and audience tune the sounds into the local realities of rocks, hills, trees, people... Didgeridoos, as any musical instruments, may be played like people and birds tuning their notes to local energies, keeping their tonal qualities the same...although the sounds of birds, if slowed down, are vastly more complex than they seem to be.

A strong high-frequency resonance, in a variable system, can evoke variable-pitched lower-resonances in nearby systems. Resonance is by synchrony, harmony, regardless of the fundamental frequency.  For example, one of the reasons birds such as magpies sing continuous cadences is so standing-waves can happen at frequencies depending on the birds' locations, and be loud for at least one frequency in each cadence; and the bird is likely causing the sun to rise.

Overblowing a wind instrument can produce many harmonics higher than the fundamental. Embouchure-related resonance adjustments can vary pitch continuously and by half-notes. The amount of air flow needed, for different notes, can be almost the same for higher notes as for the fundamental; so "overblow" is somewhat an inaccurate word when regarding resonance-adjustment techniques.

The bell is helping the pipe to play many notes rather than just its most natural resonance. The bell is like an exponential horn for an old wind-up gramophone. The bell and added length amplify, as shown in one of the below videos showing a short pipe without a bell. The bell is an example of how pipes are less than absolutely fixed to length for their best resonance when combined with other resonant and/or energy-source systems.

Another way of explaining how a didge/trumpet/whatever can play lots of notes (rather than one-per-length-change)is to consider how the exponential horn on a gramophone can help any note on the record get out into the air. Then add the idea that a didge is still a tube with only a slight tendency to resonate on its own. So, when something providing the energy has a strong resonance then the didge follows that additional to its small tendency to have only a one-note resonance.

Everything with some flexibility/elasticity has a tendency to resonate at some frequency. Given a momentary input of energy, that energy will turn into heat in stages with their timing dependent on many factors such as length, width and whether a pipe is open at both ends or closed at one end (and like a bell rings until the energy turns into sound then/and heat). The say "natural" resonance of a system (such as a pipe) is its resonance when on its own. When something resonant like a pipe, is combined with other resonant systems, then the set which provides the most energy and has the most efficient resonance dominates the co-produced frequencies. A didgeridoo, by getting its resonance from the person interacting with the pipe-length-related resonance (and their surroundings generally) acts more like an amplifier than a closed tube. Didgeridoos can resonate with dominant energy-source resonances within the musician, the audience and their physical surroundings; and all "chi" "qi" spiritual-physical energies.

For resonance-based didge playing, some of the factors in the resonances of voice (vocal chords, nasal cavity, chest...) are replaced or augmented by such as the lips, tongue and the didge. Part of learning, for resonance embouchure-control, is to listen and feel the sound characteristics change for the mouth when open compared with the teeth held together.

The learning-curve, of a fixed-length tube instrument, is difficult for getting past a one-or-two-notes ceiling. The limit is imaginary. We learn what we know we should know.

"Circular breathing" helps keep the notes continuous, for resonances to be maintained so notes changes mathematically related to a natural scale. When familiar with feelings associated with pitch control, progress speeds up; like learning to sing or, if one has learned to sing, as one may learn to whistle.

An exponential horn, for a didge; might be easier for multi-key play than a long tube with a short bell-like horn; but likely to have one section too dominant and the other too passive. Such a didge is likely to have less harmonics, to sound more like a tuba than a didgeridoo. The long length of drain-pipe had beautiful resonances; it responded with subtle frequency changes just as easily as my new didge that has a bell. Similarly, cardboard mailing tubes resonate well (with lacquer to harden inside edges they'll be rich-sounding didgeridoos).

Didgeridoos can play any note a human voice can play, and more. Search (Wikipedia has a great article) the various theories about how wind instrument sounds happen; notice how publications don't/rarely use the word "resonance" yet that is what is being controlled by changes in mouth shape, tongue, cheeks... I had the joy, for example, of playing a Tibetan long horn made of brass, decorated; that, also, can play more than one note. I believe the Tibetan horn, while keeping the length fixed, can be fine tuned with the surrounding physical features and energy frequencies.

A bugle can play more than three notes; yet some believe a didge can play only about three notes. An example of one belief-system's limitations, for the number and type of notes a didge can play, regards the three as the fundamental, plus a "toot" natural harmonic higher, and one note an octave below the fundamental. A didge can be induced to play continuous changes in pitch; additional to normal arpeggio-type natural harmonics that are mathematically accurately related to the fundamental.

Another phenomenon, using the "co-resonance" approach to embouchure and interaction with an external instrument, regards one's body as external to one's-self only partly and equal to the "instrument" as being part of oneself. The didge can be locked into a key then it easily follows that for subsequent notes. I've read a professorial-level article (mercifully forgotten the reference) proclaiming that a didge might be able to change a half note using pressure-changes! The author probably was thinking a didge pipe's frequency is fixed according to length, as for pipe-organ pipes; as organ pipe lengths have added allowances for the directional-ballistic air exiting the pipes effectively adding length before the pressure spreads and ceases to be part of the resonant system related to pipe-length.  The best examples I've found, of genuine and accurate scientific publications re the physics of music and acoustics, are here: http://www.phys.unsw.edu.au/music/index.html

A didge, on its own, resonates as if it is a fixed length, only if the energy source's frequency is locked to the natural frequency of the didge according to its length and width (which affects the virtual additional length at the open end). If the energy-source is resonant in its own right and compatible enough to form a co-dependent resonant system with the didge, then the didge and second resonant system form a co-dependent resonance with a mutual set of frequencies according to the balance of their acoustic impedances. This means that one may have complete control over the frequency of the didge (and/or voice, bugle, Tibetan horn, trumpet...) by one's internal resonant systems being completely controlled by one's say "spirit", will, intent... That's the same as one's body-distributed "brain" system reacting as it does, faster than light, to enable one's intent to e.g. listen and/or speak, to happen instantly one hears sounds that communicate.

The same principle applies to musical instruments as, for example after a stroke one "can't get out" any more: Regard any instrument as an extension of one's brain/body functions; so control these first and the musical/whatever instrument does what it does best, responsively, interactively. We're made to interact with living things; and everything that has individuality is alive — according to how the living being within it intends to experience that type of life.

Varying the frequency is easier for notes that are whole-number mathematically related to the natural resonance of the system. Varying frequencies, for in-between or continuous notes, involves compensations for the changes in acoustic impedance of both systems; relative to the required notes. The amount of air and energy needed, to play continuous or half-note scales, on a didge, varies with each note according to how well it matches the easiest resonances to control; so playing an arpeggio is easier than playing half-notes or completely off-key deliberately and accurately.

A musical instrument, and a person, have individual tendencies to resonate. Both have resonances that stop quickly when the energy-source stops. The didge has slightly more tendency to hang onto notes than the voice. The didge can't change; the musician can. When the musician uses voice resonance to talk and sing, changes must happen quickly. The didge keeps resonating, after the energy-input stops, only slightly longer than a human voice; that's enough for a mutual resonance to last long enough for the person to refresh the air in the mouth cavity. The combined mutual resonance, between the human and the closed tube, can be any frequency within their mutual range. The opposite applies to the presumptions regarding all wind instruments of fixed length: the instrument's length may determine the pitch when the player lets the instrument's length be the deciding factor; and when the player determines the pitch, then the team can produce sounds of various frequencies and matching tonal qualities, as living beings making natural sounds

Musical instruments, like living voices, have low "Q" in terms of energy in relative to circulation. Living systems have efficiency for turning energy into sound. Human/living voices, the didgeridoo and many other musical instruments have wondrous efficiency at turning intent-type energy into sound energy. The "Q" factor in the human voice is low --- otherwise we'd be ringing like a bell until the sounds (and striking energy) all turned into heat; instead the human voice has huge efficiency for turning intent into sound.

A didgeridoo's own resonance abilities add "Q"  to keep ringing long and strongly enough to get breath into the mouth without losing resonance as the mouth-shape changes . One's interactive personal adjustments combine for mutual resonances with the didge as interactive agreements for frequencies and harmonics of the sounds. Musical instruments have low "Q"; so must constantly be refreshed with energy. The resonance of the didge and surroundings, with the musicians affecting the resonance, can channel into multi-dimensional energies for such as communications, healing and envigoration. I believe in resonance for gathering energy. We get energy by interaction.

Didgeridoos apply resonances for life energy by one note tuning with surroundings. Resonances are enhanced by systems synchronizing accurately. When in collaboration with the didge rather than in control of the didge, the didge becomes an interactive radiator enhancing vocal effects. I'm writing some notes about how to learn this way of "co-resonance" with wind instruments. The first page is here:  Didge_Learning_Resonance_Method.html

The recording just below, by a Sony ICD-SX700 (that died aged three) is of a plastic drain-pipe played as a didgeridoo (it had a pipe-diameter-change joint as a mouthpiece). The recording suits being loud and stacked to add grunt and likely beat-frequencies. Start the top player and the two players below at different times. Or download the .mp3 and play it in a few players starting at different times and, if possible, in different channels additional to their ordinary stereo nature; and if you get a binaural effect that can be hypnotic/out-of-body...


Download the above mp3 track.

Didge exercise on YouTube (below) show me struggling to learn this new technique well enough to be musical when the technique is reliable enough.

I made some videos with Steven Guth. We agreed on the production aims, theme, plot... and Steven sent the voice and video clips. I cut and shuffled the clips to fit our ideas and tell a story; Steven composed his commentary to fit the video and in some of the videos I cut-pasted the words together and Steven fitted the video sequence... For the Barwang video I added a didge track to start where it does; one take; I'm proud of it. A psychedelic didge-track, processed, was added last; to the beginning of the didge track (not in the mp3 here). We did six videos like that; a crazy way to make videos; good fun!

© David Beale 2014

A random page on the same VPS.

Videos of David Beale practicing (drills) with the didgeridoo

Videos of advanced learning-practicing exercises for the didgeridoo

The video clips show some unusual didgeridoo techniques being learned; just as examples of what can be done. The Barwang video used these methods in its background sounds track.

This video was recorded by a Zoom Q4.

Download the mp3 6.5MB 48kHz 320kbps


Download the mp3 22MB 48kHz 320kbps


This video was recorded by a Canon G11.


This video (and others on this page) was recorded by a Panasonic NV-gs300 in fluoro light.






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