Additive Synthesis

The basic idea of the “Additive Synthesis” is, to generate a sound wave by adding harmonic overtones (= integer multiples of a root wave). In principle every harmonic sound with any timbre can be produced this way.

But nature is a little more tricky. On one hand no sound has a constant overtone spectrum. In the most cases the higher overtones fade out faster than the lower, so that a sound start bright and ends dull.

On the other hand two or more waves with slightly different frequencies can superpose and produce nice humming interference's.

 So the “Advanced Additive Synthesis” uses several (1-4) slightly detuned oscillators with fading overtone spectra to produce natural and interesting sounds.

You can set an overtone spectrum manually with the volume sliders or you can construct it by selection rules or you can generate it automatically with FFT (Fourier-Transformation) of a natural sound.

Adding the overtones is not the only “Method” to generate Tones. You can also alternatively add and subtract overtones or multiply them (=Ring Modulation) or use to modulate a sine wave (=FM Synthesis). If you have an overtone spectrum you can modify it by different algorithms to change the brightness and it is also possible to use saw- or square-waves instead of sine waves to generate shrill sounds. Try the different “Methods” and hear the results.

With the help of construction rules you can quickly create new waves. For example, if you add all overtones with decreasing volume (A= 1/n), then you will get a saw-wave. If you add all uneven (1,3,5,7 …) overtones with decreasing volume, you will get a square-wave (A=1/n) or a triangle-wave (A=1/n/n). If you add not all odd overtones but only a few (<8), then you will get a soft square-wave and so on.

You can also record a natural sound (from an instrument) with a microphone (or load a *.wav or *.mp3 sample file) and let it automatically analyze by FFT-Transformation and resynthesize (Fourier-Synthesis) to get an overtone spectrum that sounds similar to this natural wave.