"One cannot synthesize what one cannot analyze" (Second law of Synthesis)
 

My earlier column on the Gamelan got me a lot of positive responses.
Most readers tried the patch and found it, aurally, very interesting.

The majority of us synthesists, have always had a fascination for percussive musical instruments of Ethnic origins : their awkward scales and weird
timbres are particularly suitable for e-music production needs.

In this article, we will cover another interesting percussive instrument : the Balafong . Contrary to the Gamelan, which belongs to the family of musical instruments called "Metallophones", the Balafong belongs to the family of musical instruments called "Wood Harmonicons" (ref: H.Helmholtz).
 

Sympathetic Resonant Chambers

Unlike the Gamelan - which has a gong-like timbre, rich in harmonics the Balafong's timbre is a sort of hybrid-cross between a dull sounding
marimba and a muffled wooden xylophone. Typically, players of the Balafong produce tones by striking the wooden sounding bars with hard wooden mallets.

Each sounding bar is attached to a trapezoidal wooden frame by small strings. Under the frame, each wooden bar is equipped with resonating
Gourds : they act as sympathetic resonance chambers and amplifiers (some African Balafong are equipped with coconut shells, containing some fine pellets : each strike of the mallet produces a typical granular and resonant sound in the process).

This instrument is played in Western, Central and South-Africa, but is also found in South-East Asia : this might explain the cultural differences
in tuning and pitch perceptions of the various musical scales used.

The illustration below shows, in Figure 1, a table of Balafong scales, in cents, compiled and analyzed by acoustician Hermann Helmholtz,
during the middle of the 19th Century. Regretfully, the countries of origin of the two Balafong scales from Western Africa are not known. Nor is the one pentatonic scale labeled as being of a South-Pacific origin!

I draw your attention to the oddly Siamese scale :the two values of G+26cents and G#-29 cents are really too close together for comfort : they should never be played consecutively! I suspect, that the purpose of these two tones are to function as a pivot tone to bridge -and to differentiate- the ascending or descending part of the scale!
 
 

Patch Analysis
 

Figure 3, shows the patch of the Balafong. Although it has been implemented specifically for the Serge system, users of other synths can easily adapt it to their specific gear. This is the explanation of the patch...
A sine waveform, with a frequency of 130.81 Hz.(C3) is connected to the carrier input of ring modulator # 1, Multiplier # 2 and Serge's middle Wave Multiplier. Another sine waveform, with a frequency of 392 Hz. (G4) is then patched to the modulating signal input of ring modulator # 1.
A square waveform, with a frequency of 880 Hz. (A5) is patched to the modulating signal input of Multiplier # 2 as well as to the second input of the middle Wave Multiplier.

The two ring modulators and the wave multiplier's outputs are then mixed into a passive audio mixer, whose output is sent to two different VCF : a Serge VCFQ and a VCFS. The Low Pass outputs of each filter is then sent to VCA1 and VCA2 for final amplification.
 

A Serge TKB (Touch activated Keyboard Sequencer) -or any unquantized sequencer having 4 rows of CV outputs available simultaneously - is then used as a master controller :

Sequencer Row A : controls the three VCO's fundamental frequency (1 Volt.oct.).
Sequencer Row B : controls the two VCF's 1 Volt.oct.inputs.
Sequencer Row C : controls the resonance of the first filter VCFQ (Frequency and Q settings at 9 o'clock).
Sequencer Row D : controls the slope of the second filter VCFS (frequency pot at 9 o'clock, VC slope pot at 5 o'clock, resonance pot at 9 o 'clock),
as well as the AM/Ring ratio of Ring Modulator # 1 (VC pot at 7 o'clock) .
KP output : the Keyboard pulse to trigger the two envelopes, which are set in an anti-log configuration.
 

Tuning in cents

Using the conversion table in Figure 2, calculate the given Balafong scale and all deviations, in cents, from known musical tones. For example, to convert the # 2 scale of the Balafong from Western Africa, substract or add this scale (in cents) to the nearest number shown on the equal temperament scale (in cents) and calculate the notes deviations (in cents).
Once the correct scale has been determined, you can start tuning your VCO's.

First, connect VCO1 sine to a VCA (full VCA) and set it to the required frequency (C3=130.81Hz.). Proceed to do the same for VCO2
(G4=392 Hz.) and VCO3 (A5=880 Hz.). That done, connect sequencer output A to the 1 Volt.oct inputs of VCO1, VCO2 and VCO3.

Using an electronic tuning device, which shows the value of a given note in 100 cents increments (from -50 cents to + 50 cents), we can now start to tune all our VCO's to their final values.

As an example, let's take the Balafong scale # 2 of Western Africa : i.e C, D-48 cents, D#-13 cents, F+33 cents, G+24 cents, A-10 cents, A#+39 cents and C. The first step is C=0 Volt (no change). The second step is D-48 cents : turn the pot until the tuning device shows the
value of D then, turn the pot counter-clockwise until it reaches the bottom left of the screen (-50 cents) and fine tune it to -48 cents.

The third step is D#-13 cents : turn the pot until the tuning device shows the value of D# then, turn the pot counter-clockwise until it reaches the value of - 13 cents. Proceed with all the other steps as shown. When all VCO tunings are completed, clear your synth from all patch cords and bring your
VCA pot back to its 12 o'clock position..

Complete the Balafong patch, as outlined in Figure 3, while being extremely careful not to touch your VCO's fundamental frequencies nor your Sequencer Row A pots..
 

Note: To have a different pallette of colors for the complex tones, I have used a Serge ring modulator, with AM/Ring VC functions, for VCO1 and VCO2 sine waveforms and a standard multiplier for the sine/square waveforms.
The Wave Multiplier function is to reinforce the fundamental frequency, while adding a complex granular tone into the mix.

The Balafong being a highly non-linear instrument : the brightness/resonance ratio has to be set individually for each tone (this ratio is set by Sequencer rows B and C). Needless to say, by using high resonance (Q) with a filter initial frequency set very low, might contribute to some unwanted resonance clipping!

I have got good results with a muffled lowest tone C (set sequencer output B to 9 o'clock and sequencer output C and D to 10 o' clock).
Tone D should also be muffled (10 o'clock) but with a higher resonance (11 o' clock). Tone D#, G, A# should be brighter (11 o'clock) with more resonance (12 o 'clock). The last upper tone C should be set at 10 o 'clock but with a higher resonance (2 o' clock).

Complete your patch as shown, and continue to tweak all pots until you are satisfied with the results...

Enjoy!
 

André Stordeur
12.20.2002