Subtractive synthesis, also known as analog synthesis, emerged around 1960—the same time the analog synthesizers did. Many of these synthesizers use the analog technique to produce sounds. The kind we’re talking about today here involves three main components: oscillator, filter, and amplifier.
The Components of Subtractive Synthesis
In the following paragraphs we’ll explain the three of the previously mentioned components.
The Oscillator
The oscillator creates a sound processed by a filter and sent to an amp to control its volume. Oscillators involve two main parameters that the user can alter and control: waveform and pitch. The waveform is a particular structure of the produced soundwave and can fall under four different types: sine, saw, square, and triangle. On the one hand, the sine waveform involves a fundamental tone and it has no harmonics. On the other, the saw waveform involves high harmonics and a very buzzy sound.
Please note that pitch, frequency, and speed are interchangeable, generally. The main difference between them is that the frequency is measured in Hertz, whereas the pitch is represented in terms of notes and octaves.
The Filter
The filter works by removing parts of the frequency spectrum. First, it defines the cutoff point. Then, depending on the selected filter type, it removes the frequencies that fall above, below, or around the cutoff point.
Resonance also includes a filter. Resonance operates by increasing the frequencies that are close to the cutoff point. When this happens, the operation of the filter is emphasized.
The Amplifier
This component is the easiest to explain. The amplifier controls the volume of the sound, leading to envelope modulation.
There are several ways in which the user has control over these parameters. The most common one is to use an envelope generator, as well as a low-frequency oscillator (LFO), for both filter and amplifier components. A low-frequency oscillator transmits values instead of sounds, and it works on low frequencies. The LFO is capable of controlling both the waveform and the frequency. An envelope generator has four main points: attack, decay, sustain, and release. This device can control volume as well as multiplying its values in a range of 0 to 1.
