A synthesizer, in general, has the same two components as virtually any other instrument: a generator and a resonator. To provide an analogy, let’s consider the violin. On the violin, the strings and bow are the generators and the body of the instrument is the resonator. Likewise, the oscillator on a synthesizer is the generator, while the filter is the resonator.

About the analog synthesizer

Analog synthesizers produce sounds by altering electric voltages. The oscillator shapes the voltage to generate a constant pitch at a specific frequency, determining the fundamental waveform that will be processed further. Piano-style keys, a moving pitch wheel, or another tool on the synthesizer’s interface can control the oscillator.

The oscillator sends the signal to the filter, and the performer uses knobs and dials on it to adjust settings, such as removing or accentuating particular frequencies.

Sound travels through the filter to the amplifier, which regulates the volume. The amplifier often contains a set of envelope controls that aid in determining the nuances in volume level throughout the length of a note.

Each of the described functions group together into a module or specialized unit in the analog synthesizer. These modules generate a certain signal or process it in a specific manner. By linking them together, the performer may layer, process, and transform the sounds into something completely new and unique.

Types of synthesis

Synthesizers generate audio in a variety of ways, which define synthesis types. One of the most common types of them is subtractive synthesis. Briefly, we start with a waveform such as sawtooth or sine, and subtract components to achieve the desired tone.

A LFO, or low-frequency oscillator, generates waveforms used to modify parameters such as oscillator pitch. Voltage-controlled filters, or VCFs, “shape” the frequency-domain sound generated by the oscillators. These are important for subtractive synthesis. Filters are especially essential in this type of synthesis. This is because they are designed to pass some frequency regions or bands unattenuated, while drastically attenuating, or subtracting others. The low-pass filter is the most commonly used. However, band-pass filters, band-reject filters, and high-pass filters are also common.

Envelopes define the way sounds change over time. They may change characteristics like amplitude (volume), filters (frequencies), or pitch. The ADSR (attack, decay, sustain, release) envelope is the most common.

Arpeggiators and controls

An arpeggiator is a synthesizer component that automatically steps through a sequence of notes depending on an input chord. This results in an arpeggio. The notes often travel to a MIDI sequencer for recording and editing. An arpeggiator may include controls for speed, range, and the sequence in which the notes play; upwards, downwards, or randomly. More sophisticated arpeggiators allow the user to step through a pre-programmed sequence of notes or to perform many arpeggios at the same time. Some allow a sustained pattern even after releasing keys, allowing a sequence of arpeggio patterns to build up over time. Arpeggiators also appear in software sequencers.

Synthesizers are frequently controlled via electronic digital keyboards or MIDI controller keyboards, which can be integrated into the synthesizer unit or connected through CV/gate, USB, or MIDI connections. Keyboards may have expressive features such as velocity sensitivity and aftertouch, which allow for greater control over the sound.