How Do Analog Synths Work? – Oscillators, Filters & Envelopes Explained

How Do Analog Synths Work? |

All synths, irrespective of their brands, consisting of a handful of essential components that work together to create a sound. These components include an oscillator to generate a waveform and alter its pitch, an amplifier to control the signal volume, a modulator to produce effects, and a filter to change the timbre by carving out specific wave frequencies. But How Do Analog Synths Work?

The voltage coming from a power source generates a waveform by oscillating electrons. Since every waveform has a different sound, most of the synths come with an option to select the type of wave shape from the following four options: sine wave, sawtooth waves, triangle waves, and square waves.

Each shape has a unique set of tonal characteristics and can be layered or combined to create various sounds:

  • Oscillator

The oscillator of the synth is the primary source of sound. Users can pass this sound through one or a few signal modulators to produce mixed results. The filter is responsible for modifying timber by blocking a few frequencies and letting others pass. A synth can also manipulate the size of a signal by adjusting Attack, Decay, Sustain & Release times.

Compare it to the guitar string pluck. When a guitarist plucks a string, it causes the string to vibrate enough to produce a signal at a constant rate. Oscillators work on a similar principle. 

The oscillator section of a synth also controls the pitch or the frequency, i.e., the speed at which vibration occurs, measured in Hertz. The lower the frequency of an oscillation, the lower the pitch of the note that it generates. If you double the audio signal frequency, its note will go up an octave and vice versa. 

How To Use A Synth: Part I - The Oscillator Section
  • Filter

The synth filter is responsible for modifying timber by blocking a few frequencies and letting others pass.  Have you ever noticed how a piano and trumpet sound very different even if you play them at the same pitch? That is because of the sound’s timbre, determined by the prominent or lacking points in its overall frequency spectrum. 

A sine wave is considered a single frequency, but every other sound collects multiple frequencies that join together to create a dominant pitch. This is why a C chord on your guitar sounds more like a C even though G and E notes are also played. All this is what you call harmonics; you can’t hear them as discrete pitches but overtones that grant them their unique timbre.

How To Use A Synth Part III - The Filter Section
  • Amplifier and Envelope Generator

You are probably aware that an amplifier controls the volume by making the signal bigger and louder. But what you don’t know is it also modifies the amplitude of the signal with time, how quickly the signal hits its peak loudness, and how long it is sustained.

Imagine the sound coming from banging the piano and comparing it to the sound of a violin string played softly and slowly! The piano would be loud, short, and abrupt, while the violin would not peak in volume as quickly and die down as soon the player stopped bowing. Each instrument has a set of amplitude characteristics that we can quantify, and the same can be said of analog synths.

The envelope generator manages the loudness contours that you often notice in analog synths. 

The most commonly known components of an envelope are known as ADSR:

  • Attack

This control decides how quickly your signal occurs once you trigger it. A fast attack equals a quick onset, while a slower attack does the opposite. The faster your attack time, the brighter your signal will generally appear.

  • Decay

Decay determines how long a signal will take to fade out once triggered. The greater your decay, the more present your signal will be until the point that it fades out.

  • Sustain

Sustain controls how much a note or signal will hold once it has been triggered. The control ties the attack and decay together and is often used to set the overall thickness or weight.

  • Release

This parameter lets you decide the total timespan of your signal. Setting a quicker release time shortens the overall signal’s length while increasing the release time will result in more extended.

Adjust these contours, and you will change the entire character of a sound.

Envelopes tutorial -
  • Modulation

There are many types of modulating devices, each with the ability to alter the sonic properties differently. A great example of these units is the low-frequency oscillator or the LFO. This device oscillates a signal at a frequency lower than the human ear can hear. It is not there to produce sound but to modulate other components of a synth.

For example, a modulator can work hand in hand with an oscillator to create vibrato by jiggling the pitch or tremolo by affecting the volume. Another example of LFO modulation is filter oscillation, such as those found in sounds like modern wobble bass.

Producers enjoy the modulation purposes of synthesis as they add a truly unique element to their compositions. Modulation offers you expressional dynamics that could not otherwise be recreated by a human or other means. You can also apply multiple modulations to a signal at one time and have them be time-aligned with each other or linked to an external source.

Intro To Synthesis Part 6: Modulation and LFO | Reverb Learn to Play

How Does a Synthesizer Produce Sound?

Synthesizers produce sound using sound wave generators known as oscillators. These sound waves can then be layered and manipulated to create a large variety of sounds and tonesAnalog synthesizers consist primarily of a series of electronic modules that either generate or affect sound waves.

Many analog synthesizers will allow you to control the shape and movement in a few ways. For example, most synthesizers will let you control the size or amplitude of a waveform. Another example of signal modulation is frequency control. Adjusting the frequency of a signal will determine how the speed at which it occurs and, thus, control a signal’s pitch. 

A synth’s capabilities and the overall sound will depend on the analog circuitry used for its design. Analog synthesizer designs are constantly being revisited, modified, or upgraded, and their capacity for evolution is a large part of what makes analog synthesis so appealing. 


Early analog synthesizers were made up of modular units that could be patched into each other and resembled the machinery used by telephone service operators of the 1940s. There were no keyboards or drum pads in these old synths. Instead, engineers produced sounds by adjusting dials and parameters on voltage controllers and routing them into each other. Many of these synths are still used in modern-day music production. 

How Do You Record An Analog Synth?

You can capture the audio by patching your synth’s output channels into a recording interface’s input. Synthesizers generally come with two stereo output channels that you can route into a recording device for capture. 

Alternatively, you can route your synth into another analog recording device, such as a reel to reel or tape machine, should you have access to do so. 

The next option is MIDI capture. Analog synthesizers will often have MIDI channels that you can use to either send or receive musical information. For example, you can send the midi of a chord sequence from your synth into a DAW like Logic or Ableton via a midi interface.

The chord sequence’s midi information will consist of the pitch, timing, and expressional parameters such as velocity that you can then implement on another digital instrument.  You can send midi information into a synthesizer to implement on a particular sound or patch of your preference in the same breath.


Routing the metronome of composition from your DAW into an analog synth’s midi will help any modulations you apply to stay in time with your song. Many producers or engineers will use this technique before selecting their synth patches to avoid having to struggle with any timing-related issues during composing, mixing, or arranging. 

Analog Synths vs. Digital Synths What’s The Difference?

An analog synth is defined by its electromechanical construction and design. Its essential concept is that it produces sound by generating an electronic signal which you can modify. Digital synths tend to carry more presets and assignability thanks to digital music technology advances in the modern era. 

Analog synthesizers and digital synthesizers each provide a few advantages and disadvantages to users. Choosing between them will come down to a matter of personal taste and musical circumstance. 

Because of how they produce sound, analog sound waves usually have warmer or more lush signals than digital synths. Their manufacturing is costly, making digital synths slightly more accessible to the everyday producer. 

 Digital synths also generate more stable and consistent instances of a signal as opposed to analog synths. Digital synths tend to offer more audio manipulation options, but their sounds are still mostly modeled on or are derivatives of analog machines.

Final Thoughts

Analog synthesizer technology has been an ever-growing industry for close to over a century. These marvelous machines have been an integral part of both traditional and modern music production. Understanding how analog synthesizers work will not only help you grasp the essentials of how sound is generated from a scientific point of view but will also provide you with invaluable musical knowledge as a composer or producer.

There is a dizzying bevy of analog synths to explore and experience, and we hope that this article encourages you to do just that. Thanks for reading our article on how analog synthesizers work. 

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