Subtractive is the most common method that gave birth to the concept of sound synthesis. And is also one of the most popular synthesis types of all, perhaps due to its inherent simplicity and application.

This type of synthesis is a very simple signal chain of an oscillator (or the combination of multiple oscillators) running through a filter (EQ curve) which is then sent to an amplifier for gain staging and ADSR (attack, decay, sustain and release) for controlling the envelope response. The harmonics present within the oscillators tones can be whittled into harmonic structures that mirror those of actual instruments. This method is very easy to achieve in both analog and digital realms and can be used to create numerous (possibly infinite) instruments, effects, and sounds.

The analog subtractive synthesizer was initially designed for this purpose–as an alternative to hiring musicians to play on recordings, however, it quickly morphed into its own instrument, creating various sounds never before made by any acoustic instrument.

Subtractive synthesis is the most closely associated with the analog synthesizers of the ‘60s and ‘70s.  In which the harmonics of simple waveforms, such as the ones previously mentioned, are attenuated with a voltage-controlled resonant low-pass filter.

Some of the Vintage synths most known in this type are the Minimoog, and the Korg Ms-20, maybe you recognize them!

topmusicarts/4-main-types-of-synthesis-explained-wavetable-fm-additive-and-subtractive

Figure 5.1 Sine, square, triangle, and sawtooth waveforms

An oscillator is a repeating waveform with a fundamental frequency and peak amplitude and it forms the basis of most popular synthesis techniques today. Aside from the frequency or pitch of the oscillator and its amplitude, one of the most important features is the shape of its waveform. The time-domain waveforms in Fig. 5.1 show the four most commonly used oscillator waveforms. Although it is possible to use all kinds of unique shapes, these four each serve a range of functions that are suited to a range of different synthesis techniques; ranging from the smooth, plain sound of a sine wave, to the harmonically rich buzz of a sawtooth wave.

Oscillators are generally controlled by a keyboard synthesiser or MIDI protocol device. A key press will result in a MIDI note value which will be converted to a frequency value (Hz) that the oscillator will accept as its input, and the waveform period will repeat accordingly to the specified frequency. From here, the sound can be processed or manipulated in a variety of ways in the synthesizer or program to enrich or modify the sound further. weki