Additive synthesis

The additive synthesis is a method of synthetic sound generation and is used for example in electronic musical instruments such as synthesizers and drawbar organs. In the additive synthesis of the sound, in contrast to subtractive synthesis is not produced by the fact that it filters out the unwanted components from an overtone spectrum, but by the sound created by assembling the desired harmonic partials.

Principle of operation

The additive synthesis is based on the theorem of the French mathematician Fourier (1768-1830), that every imaginable sound can be generated from an appropriate mixture of many individual elementary sine waves (Fourier synthesis). To create a complex sound are many partials, which typically need to be dynamically controlled by envelopes. Would you therefore want to affect 512 partials each complete with ADSR envelope to get to 2048 parameters, which makes the operation and handling quite cumbersome. This creates an extreme hardware or computational effort. The Additive synthesis can by its analytical process as opposed to subtractive synthesis very precise sound characteristics to.

Electric Organs

A simple early proponent of this type of synthesis is the drawbar. It has several drawbars. Each drawbar represents a partial of the overtone series in sine form, which can be controlled by pulling out or pushing in the drawbar in the volume. The classic drawbar organ with 9 drawbars per manual features.

Synthesizer

As one of the first digital synthesizer, the Synclavier used additive synthesis. Later For the mass market, followed by Kawai Synthesizer. The tone generator of the Kawai K5000 introduced the first 128 partials as sine waves available, the respective volume of the sound part has been retrieved from memory. The programming of sounds by means of this large number of partials is only possible thanks to some built-in functions that allow you to group partials.

Dissemination

To understand the additive synthesis knowledge of acoustics and music theory are very helpful in terms of the partial tone series. The additive synthesis is difficult to understand intuitively than eg subtractive synthesis. This may, in addition to the more complex technical feasibility, be a reason for the rather low incidence of this synthesis method.

Another purely built on sinusoids synthesis method is the FM synthesis.