Synthesizer Oscillators: Everything You Need To Know
What is an oscillator
A synthesizer oscillator is one of the parts of a synthesizer that generates sound.
A sound is produced by repeating a waveform, like a sine wave or a square wave. The oscillator is responsible for creating the raw audio signal. This signal can then be shaped and modified by other parts of the synthesizer to create different sounds.
Some synthesizers have more than one oscillator, which can be combined to create more complex and interesting sounds.
When a synthesizer has one oscillator, we call this a monophonic synthesizer (mono synth).
When a synthesizer has multiple oscillators we call this a polyphonic synthesizer (poly synth).
Waveforms
When you make a sound, the air molecules around you start to vibrate. These vibrations create changes in air pressure that move through the air as a wave. A waveform is a visual representation of that sound.
A waveform is typically displayed as a graph with time on the horizontal axis and amplitude on the vertical axis (as seen below).
The amplitude of the waveform is the volume of the sound.
The shape of the waveform is the timbre or quality of the sound (how it sounds).
The frequency of a waveform tells us how often the wave goes up and down in one second. This is called a cycle and is measured using a unit called hertz (Hz).
The higher the frequency, the higher the pitch of the sound. The lower the frequency, the lower the pitch.
In the image below, you can see notes and their corresponding frequencies. You can find the frequencies of all keyboard notes here.
The note C4 has another color, as C4 is often called “Middle C”. This is because it is roughly in the middle of the keyboard.
Sine wave
Sine waves are one the most basic types of waveforms. They are known for having a smooth and rounded shape.
They produce a pure, smooth tone that is often used as a reference point for other waveforms (as waveforms can be morphed).
Sine waves are often preferred for their simplicity and clarity, as they produce a pure, non-harmonic tone that is relatively free from overtones and harmonics.
Timbre
- Resonant
- Pure
- Smooth
Frequently used for
- Sub bass
- Kicks
- Whistles and flutes
Square wave
Square waves also belong to the family of basic waveform types, as it basically is a distorted version of a sine wave. They have a sharp, angular shape and produce a bright and buzzing sound. Square waves are also called pulse waves.
They are often used to create bass and lead sounds. Many people have heard square waves in 8-bit video games, as they were commonly used on their soundtracks.
Timbre
- Bright
- Buzzy
- Rich
Frequently used for
- Distorted bass
- Clarinet sounds
- Percussive sound effects
- Retro 8-bit music
Saw wave
Sawtooth waves have a saw-like shape and produce a rich, harmonically complex sound. They are often used to create strings, pads and leads.
Saw waves get used a lot in electronic music production as they can be used for almost any type of sound, such as leads and bass. They can also cut through the mix because of their bright timbre.
Timbre
- Sharp
- Bright
Frequently used for
- Leads
- Brass sounds
- Bass
- String pads
Triangle wave
Triangle waves have a (you guessed it) triangular shape and produce a mellow and hollow sound. They are often used to create bell-like tones.
Timbre
- Hollow
- Mellow
Frequently used for
- Leads
- Pads
Analog and Digital Oscillators
When dealing with synthesis you can either use hardware or software synthesizers. The oscillators in these types of synthesizers work differently. There are three main types of oscillators you will find in synthesizers, which will be covered here.
Analog Oscillators
Analog oscillators use electronic circuits to generate signals. Analog oscillators are always physical hardware and are slightly less stable than digital oscillators. This is why many music producers favor analog synthesizers, as they have a more natural sound.
Voltage Controlled Oscillators (VCO)
Voltage Controlled Oscillators are oscillators that generate sound based on electronic circuits. They are completely analog, meaning there are no digital components involved in the creation of the sound. They are widely used and are in some of the most famous synthesizers.
One thing you should keep in mind is that VCOs drift over time, causing the oscillator to gradually go out of tune. This happens because of small imperfections and changes in for example voltage and room temperature. This is why many people find that VCOs sound more natural and organic than digital oscillators.
It is also important to let VCO warm up before your start using it. It is recommended to let a VCO warm up for about 20 to 30 minutes.
Digitally Controlled Oscillators (DCO)
Digitally Controlled Oscillators are oscillators that generate sound based on electronic circuits in combination with digital components. The main reason DCOs were invented was to avoid oscillator drift. They are also much more precise in generating a signal on a specific frequency.
The sound a DCO generates is still analog, but the pitch and waveform are much more precise than the sound VCOs generate.
Pipe Organ Range Explained
The classic Moog Model D also uses pipe organ range
It is common for analog synthesizers to display the pitch range of the oscillator in pipe organ range. The range then is expressed in inches, such as: 32”, 16”, 8”, 4” and 2”. 8” is equal to middle C (C4) on the keyboard.
Pipe organ range comes from pipe organs, and the pitch is displayed in inches because to lower the pitch by an octave, the pipe had to double in length.
Digital Oscillators
Digital oscillators are oscillators that generate sound based on mathematical algorithms. They are very stable and can perfectly generate a waveform. Because of this they can create much more complicated waveforms than VCOs and DCOs.
All digital synthesizers use digital oscillators. There are some digital synthesizers though that emulate analog synthesizers. This basically means that the manufacturer tries to recreate the sound of the analog synthesizer.
Digital oscillators are also the most used type of oscillators. This is because all DAWs include digital synthesizers and there are also a lot of free synth VSTs.
After one decade of fiddling around with synthesizers and music production, I figured it would be time to share some of my knowledge. Being a synth enthusiast has resulted in me having more synthesizers than I probably should have, but I just tell myself I need them. I am always open to chat about music, so just reach out!