Sound Spectrum and Playing styles

The sound produced by the didgeridoo is a mixture of timbres. It is a rich and complex sound that many would call organic. This complexity is a product of the structure of the instrument on one hand, the internal structure of the mouth and throat and the coupling between these two systems.
A mastery of the instrument involves a complete control over these various elements. The degree to which these various elements contribute to the spectrum also distinguishes between different sounds. For the purpose of simplifying our discussion I will divide these into three main groups.
1. Eastern Arnhem Land
2. Western Arnhem Land
3. Balanda
To begin, and to graphically demonstrate some of the qualities of the different styles, let us look for a moment at some plots of the spectrum as a function of time for the two Arnhem Land styles. I would like to advise the reader that at the moment this is a somewhat simplified analysis. I will present a more detiailed analysis in the not too distant future.
The two samples are pieces exectuted by Darryl Dikkarna Brown (Western Arnhem Land) and Larry Gurruwiwi (Eastern Arnhem Land). The first two graphics are an analysis of the spectrum of the first minute or so of the last piece on the CD, Djalu teaches 1.

The first graphic shows the time frequency spectrum in the frequency range from 0-12 kHz. This example shows a strong accentuation of the harmonics up to about 1.5 kHz then an empty band, and then another audible band around 2.5kHz. A surprising feature of the analysis is the presence of a subdominant resonance band at around 8kHz at times also strong enough to be audible - but this is probably of artificial origin.

In this second graphic we see the same piece but changing the window size of the analysis we see more details of the range from 0 to 6kHz. Here one sees clearly the harmonics present strongly up to about 1,5 kHz, an empty band, and then a second series of harmonics, again restricted to a narrow frequency band at a frequency of about 2,5 kHz. These harmonics are distinguished from the lower harmonics by the fact that they are produced by resonances inside the mouth of the player. The lower harmonics up to 1,5 kHz are harmonics intrinsic to the instrument itself.

The second piece analysed is played by Darryl Dikkarna Brown, and is the third track of the "David Blanasi Tribute Album" by White Cockatoo.

In the next two graphics we have a similar time frequency analysis of a piece in Western Arnhem Land style. Notice here that the band of accentuated frequencies is much wider, going all the way up to 6kHz in particular with a strong band at around 3kHz. The mid frequency bands are accentuated less. This is due to a preference in Western Arnhem land to instruments that have less mid harmonics, allowing the mouth harmonics to be more accentuated.

This final graphic shows the details in the 0-6 kHz band of the Western Arnhem Land style.

The balanda styles I have not analysed here and there are in fact many different varieties. If anyone would like to see an analysis of their own playing, or of someone elses playing, then please send to me a wav or similar file of good recording quality.
For the moment I have explained a few simple features of these graphs, but one can actually understand a lot about playing style by this type of analysis. The spectrum is also quite personal. The lower part is the simple spectrum of the instrument, but the high frequency part is correlated with the form of mouth and throat, and the particular way that one holds, moves and controls these during playing.

Copyright © 2006 Martin O'Loughlin