Analog Synthesizer Basics: Oscillators, Filters, Envelopes, More

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Analog Synthesizer Basics: Oscillators, Filters, Envelopes and More

If you’ve just bought your first analog or virtual analog synthesizer and are wondering what the hell all the dials and faders mean, you’ve come to the right place. While we’re not going to delve too deeply into the complicated world of synthesis, we will provide you with some basics to help you get acquainted with your instrument so that you can begin shaping your sounds.

Close-up of the Korg Monologue Monophonic Analog Synthesizer
Korg Monologue Monophonic Analog Synthesizer

We’re going to cover the key concepts behind synthesis with respect to the most common types of analog and virtual analog synthesizers, which use “subtractive synthesis” to model sound. This type of synthesis involves reducing certain sonic elements of an audio signal to change the tonal quality of the sound.

Synthesizer Key Elements

Oscillator (often labelled as VCO)

VCO via Korg Monologue

This is where it all starts; an oscillator is the sound source—the bare bones sound wave that has yet to be manipulated by synthesizer controls. Typically, you can choose which kind of sound wave you want the oscillator to produce, including a pulse/square wave, sawtooth, triangle or sine. Each type of soundwave has its own sonic characteristics. The sawtooth, for example, has a little growl or buzz compared to the plain square wave. Often, a synthesizer will have more than one oscillator, such as in the example shown above. It’s also common to have dial that can change the pitch as well as the octave range of the oscillator. Finally, the image above has a “mixer” next to the VCOs that will mix the levels of the oscillators relative to one another.

Filter

Filter via Korg Monologue

A “filter” changes the characteristics of the sound being produced by the oscillator. It modifies the tone and timbre of the instrument by removing certain elements of the harmonics (remember – subtractive synthesis). You’ll run into many types of filters depending on the type of synthesizer you’re working with. But there are a few that are more common, such as low-pass filters, high-pass filters and associated resonance modulation.

A low pass filter (LPF) reduces the higher frequencies, letting the lower frequencies pass through. In the audio world, it’s also known as a high-cut filter. It’s a great way to reduce any harshness and build warmth and body. In contrast, a high-pass filter (HPF) reduces the low frequencies, allowing the higher frequencies to pass through. You’ll often hear it used in performances when the DJ is building up the pressure of the song before it drops. Often, these above effects will be controlled by a dial labeled “Cutoff,” as is displayed in the image above and below.

The resonance knob creates a peak at the cutoff point. So instead of it being flat, the delivery grows at the edge of the cutoff. It essentially increases the slope of the filter, making the frequencies at the peak sound louder.

Moog Muse 8-Voice Analog Bi-Timbral Polyphonic Synthesizer
Moog Muse 8-Voice Analog Bi-Timbral Polyphonic Synthesizer

Low Frequency Oscillator (LFO)

LFO via Korg Monologue

Although LFOs are oscillators, they are different to the ones described above because they don’t create a new sound. Rather, they affect the sounds that already exist. An LFO is a very low frequency oscillator. It’s so low, in fact, that humans can’t hear it. But these low frequencies can have a tremendous influence on the sonic qualities of the other oscillators. In fact, LFO’s are used to modulate a vast number of different parameters, creating effects such as tremolo, pitch shifts, added textures, and even driving rhythms.

Envelope Generator

Envelope Generator via Korg Monologue

Typically, the envelope generator is used to manipulate amplitude over a period of time. The most common type of EG is an ADSR envelope. ADSR stands for the four stages of an envelope, including, attack, decay, sustain and release. And you can create a wide range of sounds by modulating each of the stages.

Attack

The attack dictates how long it takes for the note to reach its full potential. If the attack is fast, the note will sound instantly. In contrast, if the attack is slow, the volume of the note will build over time, creating a swelling effect.

Decay

The level of decay dictates how long it takes for the volume to decrease. A slow decay, for example, would lengthen the amount of time it takes for a note to fall from its highest amplitude to its sustaining volume.

Sustain

Above, we mentioned “sustaining volume”. Well, the sustain control sets the consistent amplitude of a note while it’s being pressed down. So, if you set the sustain to a low level, the attack will be more prominent. Equally, if you wanted your sound to maintain the same, consistent amplitude throughout the note, you would max the sustain level and bring the decay all the way down.

Release

The release refers to how long the note takes to quiet down after the key has been released. Long releases, for example, are commonly used to create an ethereal drone-like effect.

In this brief article we’ve covered just the basics of what an analog or virtual analog synthesizer can do. Advanced synthesizers can get a lot more complicated with respect to their features and functionality. But while sound synthesis can feel overwhelming at first, once you physically get to play around with the technology, these concepts start to become a lot more tangible. And with a bit of hands-on practice and experimentation, you’ll be on your way to shaping sounds like Pink Floyd on steroids.

To see our wide range of analog and virtual analog synthesizers, including their features, specs, and highlights, be sure to check out the detailed product pages. Or drop us a line below, and we’ll do our best to answer all your comments and questions.

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