Synthesizers By Samuel Martin

What is a Synthesizer?

A synthesizer (also called a synth) is an electronic instrument that uses electrical signals converted to sound. While most common synthesizers imitate sounds like pianos, flutes, strings, etc., they can also create new sounds that can sound totally different from any other. Synths are more often played on a musical keyboard, but you could also see them being controlled by electronic drum, wind or guitar controllers, or step sequencers.

Different types of synth controllers.

How do Synthesizers work?

Synthesizers work by creating different types of electrical signals, and then modifying them to create sounds.

Waveforms that create different types of sounds.

While there are many different types of synthesis, the most common are called Additive Synthesis, Subtractive Synthesis, and Sample-Based Synthesis.

Additive Synthesis

Creates sounds by adding together waveforms (these are usually harmonically related). By adding multiple waveforms and harmonics together, you can create extremely simple sounds, or extremely complex, large sounds. The earliest example of this type of synthesizer are the Hammond organ and Teleharmonium.

The Hammond Organ - An example of Additive Synthesis

Subtractive Synthesis

This type of sound creation is based on the filtering of harmonically rich waveforms. This is one of the most common types of synthesis, and because it is so simple, it was use in the early Moog Synthesizer. Subtractive synthesizers use an acoustic model that assumes an instrument like a piano or violin can be created approximately, by a signal generator (ie. sawtooth waves, square waves, etc.) with a filter on top of it.

The MiniMoog - An example of Subtractive Synthesis

Sample-Based Synthesis

Sample-based synthesis is created by recording a real-life instrument as a virtual waveform, and then playing back its recordings at different speed to produce different pitches. This technique in music creation is called "Sampling".

A good example of Sample-Based Synthesis is the different tones in an Electric Toy Piano.

Parts of the Synthesizer

There are many different parts of a synth that controls everything that you hear.

Electronic Oscillators - These create the raw sounds that depend upon the waveform that is being generated. Voltage-controlled oscillators (VCOs) and digital oscillators are also very common in newer models. This is the first part, and also the most important parts of the synth, because they are what actually create the sound. Without this, you would not hear anything and it would be pointless.

Low Frequency Oscillator (LFO) - This is an oscillator of adjustable frequencies that can be used or added to modulate the rhythmic sound. For example, to create vibrator or tremolo, these are essential to make these sounds. LFO's are used in most forms of synthesis.

Voltage Controlled Filter (VCF) - These "shape" the sound generated by the different oscillators in the frequency, and are most often under the control of the LFO. These are essential to subtractive synthesis, because of the nature of synthesis, and most times, there are many VCF's in one synthesizer for more control over the sound..

ADSR (Attack, Decay, Sustain, and Release) Envelopes - These provide envelope modulation to "shape" the volume of the produced note in the time domain with the most common parameters being attack, decay, sustain and release. These are used in most forms of synthesis, and can even be found on common electric keyboards to adjust the sound. ADSR control is created by envelope generators.

Voltage Controlled Amplifier (VCA) – After the final sound signal passes through the oscillators and filter and such, it runs through one or multiple VCA's. This is a preamp that amplifies/boosts the final sound, to be sent through the internal or external speaker. These are essential to the synth, because it allows the operator to control the volume by changing the voltage, before it is sent to the final speaker.

Who created Synthesizers?

Synthesizers were not created by one person specifically, but one of the earliest electric musical instrument, known to some as the musical telegraph, was invented around 1876 by an electrical engineer, Elisha Gray. He accidentally (like all other inventions on the Earth) discovered the sound creation from a vibrating electromechanical circuit, and invented the single-note oscillator, which is built commonly by hobbyists now. This instrument used steel reeds with oscillations created by strong electromagnets, which were then transmitted into a telegraph line. Gray later built a speaker into later iterations, becoming part of what we know and use today.

Elisha Gray and the Musical Telegraph

How do Synthesizers relate to Physics?

  1. To create a sound, synthesizers make sound waves (oscillations) with electricity, and you can change things like the wave type, frequency, etc.
  2. To modulate the sound, a synth uses electrical circuits like the ones that we built in class, but slightly more complicated with more parts.
  3. Lastly, the sound is finally produced through speakers, which are made out of vibrating electromagnets, as well as other parts in more complicated speakers.
Created By
Samuel Martin


Created with images by Skitterphoto - "synthesizer instrument music" • kpr2 - "synthesizer music musical instrument" • sebilden - "Korg Electribe EA-1" • garryknight - "EWI 4000S" • energylabsbr - "Waveform" • Shawn Allen - "Waveforms" • energylabsbr - "Waveform" • Creativity103 - "sinusiodal waveform" • Music Radio Creative - "Adobe Audition CS6" • Travis Goodspeed - "sos-waveform" • andyzweb - "Andrew Hammond Organ 041" • stiefkind - "Mini Moog" • brendan-c - "Octopus Piano #ds495"

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