synthesis guide 1.0

Let’s start with Eurorack. What is Eurorack?

A Eurorack synthesizer is a type of modular synthesizer that uses the Eurorack format which is a standardized system for synthesizer modules. The Eurorack format was originally specified in 1995 by Doepfer Musikelektronik (Wikipedia). The Eurorack format was not the first modular synthesizer format; many formats with different sizes and cable types preceded Eurorack before it became widely accepted as the standard format. Buchla and Serge formats are still popular and some companies continue to make modules in 5U as well, such as Noise Engineering.

Modules are measured in rack units (U) and horizontal pitch (HP). A typical eurorack module will be 3U or 3 rack units and be anywhere from 2HP to 60HP on the large end. Modular synthesizers are composed of individual modules that can be connected together using patch cables to create complex audio signals and generate a wide range of sounds.

Modular synthesizers are popular among musicians and sound designers because of their flexibility and the wide range of available modules. There are many different types of modules, including oscillators, filters, envelopes, and effects, which can be combined in various ways to create a virtually unlimited number of sounds.

In addition to their use in music, modular synthesizers are also often used in other areas, such as sound design for film and television, and experimental art installations.

Why do people love modular synthesizers?

There are several reasons why people love modular synthesizers. One of the main reasons is the flexibility and control they offer. Unlike traditional synthesizers, which have a fixed set of sounds and capabilities, modular synthesizers allow users to create their own custom synthesizer by choosing and arranging the individual modules they want to use. This allows users to create unique sounds and experiment with different configurations, making modular synthesizers a versatile and creative tool.

Another reason people love modular synthesizers is the sense of community and collaboration that surrounds them. Many modular synthesizer enthusiasts enjoy sharing their ideas and creations with others, and there are many online forums and communities where people can discuss modular synthesizers and share tips and techniques. This community aspect of modular synthesizers can be very rewarding and can lead to new friendships and collaborations.

Finally, many people enjoy the hands-on nature of modular synthesizers. Unlike traditional synthesizers, which are often controlled using buttons and knobs on the front panel, modular synthesizers require users to physically connect the modules using patch cables. This tactile approach to sound creation can be very satisfying and can provide a deeper level of engagement with the synthesizer.

What is a Patch Cable?

A patch cable is a cable used to connect different components of a synthesizer or other electronic musical instrument. The cable typically has a plug at each end, and it is used to route a signal from one part of the synthesizer to another. Most patch cables are monophonic, 3.5mm in diameter and have tip-sleeve (TS) connectors on both ends.  For example, a patch cable can be used to connect an oscillator to a filter, allowing the oscillator's signal to be processed by the filter.

Patch cables are an important part of modular synthesizers, which are synthesizers made up of separate, interchangeable modules that can be connected together using patch cables. This allows the user to create complex signal paths and create a wide range of sounds. Patch cables are also used in other types of synthesizers and electronic musical instruments, where they allow the user to route signals and control different aspects of the synthesized sound.

What is a Clock Generator and Clock Divider?

A clock generator is a device that is used to generate a periodic pulse or "clock" signal that is used to control the timing of other modules in the synthesizer. The clock generator typically has a user-adjustable rate, and it can be used to set the tempo of the synthesized sound.

A clock divider is a device that is used to divide the clock signal from the clock generator into multiple, non-integer sub-divisions. For example, a clock divider could divide the clock signal by 2, 3, 4, or any other integer or non-integer value. This allows the user to create complex and irregular rhythms and patterns in the synthesized sound.

Clock generators and clock dividers are often used together in music synthesis, allowing the user to control the tempo and rhythmic structure of the synthesized sound. They are typically used in combination with other modules, such as sequencers and envelope generators, to create complex and dynamic sounds. Clock generators and clock dividers are an important part of many synthesizers and other electronic musical instruments, and they are often used in combination with other synthesis techniques to create interesting and unique sounds.

What is a Sequencer?

A sequencer is a module that is used to generate a sequence of control signals (CV). The control signals can be used to control the pitch of an oscillator, the cutoff frequency of a filter, or other parameters of the synthesized sound. The sequence can be set by the user, and it can be played back in a variety of ways, including in a loop or in a one-time playback.

Sequencers are an important part of modular synthesizers, as they allow the user to create complex and dynamic patterns in the synthesized sound. They are often used in combination with other modules, such as oscillators and envelope generators, to create complex and evolving sounds. Sequencers can be controlled by external devices, such as a keyboard or a computer, and they can be synchronized with other elements of the synthesizer or with external audio devices.

What is Control Voltage?

Control voltage (CV) is a method for controlling synthesizers, drum machines, and other electronic musical instruments using a low-voltage electrical signal. The signal is typically generated by a keyboard or other controller, and it is used to specify pitch, amplitude, or other parameters of the synthesized sound. The use of CV allows synthesizers to be connected and controlled in complex ways, allowing for the creation of complex and dynamic sounds. It is an important part of modular synthesizers, which are synthesizers made up of separate, interchangeable modules that can be connected together using CV.

What is a Gate and Trigger?

A gate and a trigger are two related but distinct concepts.

A gate is a control signal that is used to turn a sound on and off. In a synthesizer, a gate signal is typically generated by a keyboard or other controller, and it is used to control the amplitude envelope of the synthesized sound. For example, the gate signal can be used to open and close the "gate" of the envelope generator, allowing the sound to be played only when the gate is open. This allows the user to control the duration and attack of the sound.

A trigger is a pulse-like control signal that is used to initiate some action in a synthesizer. In a drum machine, for example, a trigger signal is used to start the playback of a pre-recorded drum sound. In a synthesizer, a trigger signal can be used to reset the phase of an oscillator or to start the envelope generator at the beginning of its cycle. This allows the user to create precise, rhythmic patterns in the synthesized sound.

Gate and trigger signals are often used together in music synthesis, allowing the user to control the timing and duration of the synthesized sound. These signals are typically generated by a keyboard or other controller, and they can be used in combination with other synthesis techniques to create complex and dynamic sounds.

What is an Oscillator?

An oscillator is a device that is used to generate a periodic waveform, such as a sine wave, square wave, or sawtooth wave. The oscillator is a fundamental building block of synthesizers and other electronic musical instruments, and it is used to create the raw, fundamental sounds that are processed and shaped by other modules in the synthesizer.

Oscillators are typically controlled by a keyboard or other controller, which is used to specify the pitch of the oscillator. The waveform of the oscillator can be selected by the user, and it can be modified using various techniques, such as pulse-width modulation or frequency modulation. Oscillators are often used in combination with other modules, such as filters and envelope generators, to create complex and evolving sounds. Different types of oscillators, such as digital oscillators and analog oscillators, can be used to create a wide range of timbres and tonal qualities in the synthesized sound.

What is an LFO?

A low-frequency oscillator (LFO) is a device that is used to generate a periodic control signal at a frequency below the range of human hearing. This is not a hard rule as you can use an LFO at any rate that the module offers. The LFO is used to modulate various parameters of the synthesized sound, such as pitch, amplitude, or filter cutoff, at a sub-audible rate. This allows the user to create complex and evolving sounds, such as vibrato, tremolo, and other effects.

LFOs are typically controlled by a keyboard or other controller, which is used to specify the rate and depth of the LFO. The waveform of the LFO can be selected by the user, and it can be modified using various techniques, such as pulse-width modulation or frequency modulation. LFOs are often used in combination with other modules, such as VCAs and filters, to create complex and evolving sounds. Different types of LFOs, such as digital LFOs and analog LFOs, can be used to create a wide range of modulation effects in the synthesized sound.

What is a Filter?

A filter is a device that is used to shape the spectrum of a sound by removing or attenuating certain frequencies. Filters are an important part of synthesizers and other electronic musical instruments, and they are often used to create a wide range of timbres and tonal qualities in the synthesized sound.

There are many different types of filters, including low-pass filters, high-pass filters, band-pass filters, and band-stop filters. Each type of filter allows a different range of frequencies to pass through, and they can be used in different ways to shape the sound. For example, a low-pass filter allows low frequencies to pass through and attenuates high frequencies, creating a mellow or "dark" sound. A high-pass filter does the opposite, allowing high frequencies to pass through and attenuating low frequencies, creating a brighter or "cutting" sound.

Filters can be controlled in a number of ways, including by an envelope generator, which can be used to control the cutoff frequency of the filter over time. This allows the user to create dynamic and evolving timbres in the synthesized sound. Filters are an important part of synthesizers and other electronic musical instruments, and they are often used in combination with other synthesis techniques to create complex and interesting sounds.

What is a VCA?

A voltage-controlled amplifier (VCA) is a device that is used to control the amplitude, or loudness, of a signal using a control voltage. The VCA receives an input signal, such as the output of an oscillator, and it amplifies or attenuates the signal according to the level of the control voltage. This allows the user to control the loudness of the signal in various ways, and to create complex and dynamic sounds.

VCAs are often controlled by an envelope generator, which produces a control voltage that varies over time. This allows the user to shape the envelope of the sound, and to create sounds with attack, decay, sustain, and release characteristics. VCAs can also be controlled by other types of signals, such as a low-frequency oscillator (LFO), which can be used to modulate the amplitude of the signal in various ways. VCAs are an important part of synthesizers and other electronic musical instruments, and they are often used in combination with other synthesis techniques to create complex and interesting sounds.

What is an Envelope Generator?

An envelope generator is a device found in synthesizers and other electronic musical instruments that is used to control the amplitude, or loudness, of a sound over time. It typically has four stages: attack, decay, sustain, and release (ADSR).

The attack stage is the time it takes for the sound to reach its maximum amplitude after the envelope generator is triggered. The decay stage is the time it takes for the sound to decay from its maximum amplitude to the sustain level. The sustain level is the level at which the sound will remain as long as the envelope generator is held. The release stage is the time it takes for the sound to decay from the sustain level to silence after the envelope generator is released.

Envelope generators are often controlled by a gate or trigger signal, which is used to start and stop the envelope generator. This allows the user to control the duration and shape of the envelope, and to create a wide range of sounds with different attack, decay, sustain, and release characteristics. Envelope generators are an important part of synthesizers and other electronic musical instruments, and they are often used in combination with other synthesis techniques to create complex and dynamic sounds.

What is a Cycling Envelope?

A cycling envelope is a type of envelope that is used in sound synthesis to control the way in which a sound evolves over time. In particular, a cycling envelope is used to repeatedly apply the same set of changes to a sound, creating a repeating pattern or cycle. This is different from a traditional envelope, which typically applies a one-time change to the sound. A cycling envelope is often used in conjunction with other synthesis techniques, such as subtractive synthesis or additive synthesis, to create complex, evolving sounds. For example, a cycling envelope might be used to repeatedly apply a filter sweep to a sound, creating a rhythmic, pulsing effect. Additionally, a cycling envelope can be used to modulate other synthesis parameters, such as the pitch or timbre of a sound, to create even more complex and interesting sounds.

What is a Quantizer?

In modular synthesis, a quantizer is a module that is used to constrain the pitch of an oscillator or other signal to a specific scale or set of notes. The quantizer receives an input signal, which may be an uncontrolled or "analog" pitch, and it outputs a quantized pitch that conforms to the selected scale. This allows the user to create musical sequences that are in tune and follow a specific key or mode.

Quantizers are often used in conjunction with a sequencer, which generates a sequence of control signals that are used to control the pitch of an oscillator. The output of the sequencer is sent to the quantizer, which constrains the pitches of the oscillator to the selected scale. This allows the user to create complex and musical patterns in the synthesized sound. Quantizers can also be used with other types of signals, such as the output of an envelope generator, to create more complex and dynamic sounds.

What is a Sample and Hold?

A sample and hold (S&H) circuit is a circuit that captures the value of an input signal at a given time and holds that value until the next sample time. This can be used to create a variety of effects, such as random or stepped changes in a signal over time.

A common use of sample and hold in music synthesis is to create random or stepped variations in a control signal, such as a pitch or modulation signal. For example, a sample and hold circuit could be used to randomly vary the pitch of an oscillator, creating a "chorus" effect. Similarly, a sample and hold circuit could be used to create a stepped sequence of pitches, creating a "staircase" or "glissando" effect.

In general, sample and hold circuits are useful for creating a wide range of dynamic and unpredictable effects in music synthesis, and are often used in conjunction with other modulation and control signals to create complex and evolving sounds.

What is Subtractive Synthesis?

Subtractive synthesis is a type of sound synthesis that involves creating a complex sound by starting with a rich, harmonically complex waveform, such as a sawtooth wave or a square wave, and then using filters and other techniques to remove or "subtract" certain frequencies from the waveform. This results in a sound that is less harmonically complex but has a unique timbre that is determined by the frequencies that are removed. Subtractive synthesis is commonly used in analog synthesizers, which use electronic circuits to generate and shape the sound. In digital synthesizers, subtractive synthesis is typically achieved using software algorithms that mimic the behavior of analog circuits. Subtractive synthesis is often used to create sounds that are similar to those produced by traditional instruments, such as brass, woodwinds, and strings.

What is Wavetable Synthesis?

Wavetable synthesis is a type of sound synthesis in which digital audio is created by combining different samples of audio waveforms, known as wavetables, to produce a rich and complex sound. This is different from other forms of synthesis, such as subtractive synthesis or additive synthesis, which use different methods to generate audio. In wavetable synthesis, the wavetables themselves are created by sampling real-world sounds, such as a recording of a piano or a guitar, or by creating them using synthesis techniques. These wavetables are then combined and manipulated to create new sounds, which can be further modified using techniques such as envelopes and filters to shape the sound. Because wavetable synthesis allows for the creation of a wide range of sounds from real-world recordings, it is commonly used in digital synthesizers and music production software.

What is Additive Synthesis?

Additive synthesis is a type of sound synthesis in which a complex sound is created by combining multiple sine waves of different frequencies and amplitudes. This is in contrast to subtractive synthesis, in which a complex waveform is modified using filters to remove certain frequencies. In additive synthesis, the individual sine waves that make up the sound are called partials, and the process of combining them is called harmonic synthesis. By carefully controlling the frequencies and amplitudes of the partials, it is possible to create a wide range of sounds, from simple tones to complex, harmonically rich timbres. Additive synthesis is commonly used in digital synthesizers and music production software, and it is particularly well-suited for creating sounds that are difficult to produce using other methods, such as bell-like tones and complex, evolving timbres.

What is Physical Modeling Synthesis?

Physical modeling synthesis is a type of sound synthesis that involves using mathematical algorithms to simulate the behavior of real-world objects or instruments. This is in contrast to other forms of synthesis, such as subtractive synthesis or additive synthesis, which use different techniques to generate sound. In physical modeling synthesis, the algorithms model the physical properties of an object or instrument, such as its shape, size, and materials, as well as the way in which it vibrates to produce sound. By controlling these parameters, it is possible to create a wide range of sounds that are similar to those produced by the modeled object or instrument. Physical modeling synthesis is commonly used in digital synthesizers and music production software, and it is particularly well-suited for creating realistic simulations of acoustic instruments, such as guitars, pianos, and percussion.

What is Frequency Modulation and FM Synthesis?

Frequency modulation (FM) is a type of audio processing that can be used in music synthesis to create a wide range of interesting and unique sounds. Frequency Modulation is the technique of using one oscillator's frequency (modulator) to modulate the rate of another oscillator's frequency (carrier) often used in conjunction with an attenuator to control the amount of modulation from the modulator source.

In FM synthesis, an audio signal is used to modulate the frequency of a synthesized waveform, such as a sine wave or a square wave. This can create complex timbres and tonal effects, depending on the shape of the waveform and the characteristics of the modulating signal.

FM synthesis is often used to create percussive sounds, such as those produced by a piano or a marimba. FM synthesis can also be used to create other types of sounds, such as bells, chimes, and metallic noises.

Unlike other forms of synthesis, such as subtractive synthesis or additive synthesis, FM synthesis allows for a great deal of control over the timbre of the resulting sound. This makes it a powerful tool for musicians and sound designers, who can use it to create a wide range of sounds that are difficult or impossible to achieve with other synthesis methods.

What is Ring Modulation?

Ring modulation (RM)  is a type of audio processing that is used to create unique and interesting sounds by combining two input signals. In a ring modulator, the two input signals are mixed together using a ring of diodes. The resulting output signal has a frequency that is the sum and difference of the frequencies of the two input signals. For example, if one input signal has a frequency of 100 Hz and the other has a frequency of 300 Hz, the output signal will have a frequency of 400 Hz (the sum of the input frequencies) and a frequency of 200 Hz (the difference of the input frequencies).

The resulting output signal will be a combination of these two frequencies, with the amplitude of each frequency being determined by the amplitudes of the input signals. This can create a range of interesting and unusual sounds, and is often used in electronic music. It can also be used to create sound effects for films and other media.

What is Amplitude Modulation?

Amplitude modulation can be used in music synthesis to create a range of interesting and unique sounds. In this application, an audio signal is used to modulate the amplitude of a synthesized waveform, such as a sine wave or a square wave. This can create a wide range of timbres and tonal effects, depending on the shape of the waveform and the characteristics of the modulating signal.

One common use of AM in music synthesis is to create the "wah-wah" sound often heard in electric guitar effects. In this case, a low-frequency oscillator (LFO) is used to modulate the amplitude of the guitar signal, resulting in a sweeping effect that can be controlled by the musician. AM can also be used to create other types of effects, such as tremolo, vibrato, and phasing.

What is Phase Modulation and PM Synthesis?

Phase modulation (PM) is a type of audio processing in which the phase of a radio carrier wave is varied in response to an audio signal. This allows the transmission of audio information over the carrier wave. In PM, the phase of the modulated signal varies in proportion to the amplitude of the modulating signal. This means that the louder the audio signal, the greater the change in the phase of the modulated signal.

In PM synthesis, an audio signal is used to modulate the phase of a synthesized waveform, such as a sine wave or a square wave. This can create complex timbres and tonal effects, depending on the shape of the waveform and the characteristics of the modulating signal.

PM synthesis is often used to create sounds that are rich in harmonics, such as those produced by a stringed instrument or a brass instrument. In this case, a low-frequency oscillator (LFO) is used to modulate the phase of a higher-frequency oscillator (HFO), resulting in a complex and dynamic timbre. PM synthesis can also be used to create other types of sounds, such as percussion and noise.

Unlike other forms of synthesis, such as subtractive synthesis or additive synthesis, PM synthesis allows for a great deal of control over the timbre of the resulting sound. This makes it a powerful tool for musicians and sound designers, who can use it to create a wide range of sounds that are difficult or impossible to achieve with other synthesis methods.

What is Noise and Noise Colors?

Noise colors refer to the different timbres or tonal qualities of noise that can be generated by a synthesizer. Some synthesizers have built-in controls for selecting and shaping the noise color, allowing the user to experiment with different timbres and create unique sounds.

Pink noise, white noise, and brown noise are different types of noise that can be generated by a synthesizer and used in music synthesis.

Pink noise has a spectrum that falls off in frequency according to a power law, meaning that it has equal energy per octave. This makes it sound less harsh than white noise, and it is often used to create a sense of movement or evolution in a sound.

White noise has a flat spectrum, meaning that it has equal energy across all frequencies. This makes it sound very bright and harsh, and it is often used to create percussive or aggressive sounds.

Brown noise, also known as red noise, has a spectrum that falls off in frequency according to a steeper power law than pink noise. This makes it sound even less harsh than pink noise, and it is often used to create deep, low-frequency effects.

These different noise colors can be used in combination with other synthesis techniques to create a wide range of sounds and timbres in electronic music.

What are Attenuators and Attenuverters?

Attenuators and attenuverters are types of modules that are used to control the amplitude, or loudness, of a signal. Attenuators are used to reduce the amplitude of a signal, while attenuverters are used to invert the phase of the signal while also reducing its amplitude. These modules are often used in modular synthesizers, where they allow the user to control the level of a signal in various ways.

Attenuators are typically used to reduce the amplitude of a signal without changing its waveform. This allows the user to control the overall level of the signal, and to adjust the balance between different sounds in the synthesizer. Attenuators can be useful for fine-tuning the levels of individual modules, or for creating more complex control signals by mixing multiple signals together at different levels.

Attenuverters are similar to attenuators, but they also invert the phase of the signal as they attenuate it. This allows the user to create more complex control signals, and to modulate the amplitude of a signal in interesting ways. For example, an attenuverter can be used to invert the envelope of a sound, creating a "reverse" attack and decay. Attenuverters can also be used to create complex control signals by mixing multiple signals together at different phases and amplitudes.

What is Wave Shaping?

Wave shaping is a type of sound synthesis that involves modifying the waveform of an audio signal to create new and complex sounds. This is typically achieved by applying a mathematical function, known as a wave shaper, to the waveform of the audio signal. The shape of the wave shaper determines the character of the resulting sound, and by carefully controlling the parameters of the wave shaper, it is possible to create a wide range of timbres and tonal qualities. Wave shaping is commonly used in digital synthesizers and music production software, and it is often used in combination with other synthesis techniques, such as subtractive synthesis or additive synthesis, to create even more complex sounds. Wave shaping is particularly useful for creating sounds that have a distinctive character or texture, such as distorted guitar tones or synthesizer sounds with a sharp, aggressive edge.

What is Wave Folding?

Wave folding is a technique that is used to create complex and harmonically rich timbres by folding or folding back the waveform of an oscillator. This is typically done by using a control signal to apply a voltage to the oscillator, which causes the waveform to fold back on itself at the point where the voltage is applied. This creates new harmonics in the waveform, and it can result in a timbre that is rich in overtones and has a complex, evolving character.

Wave folding can be achieved in a number of ways, including by using a specialized wave folding module, by using a voltage-controlled amplifier (VCA) to apply the folding voltage, or by using a combination of both. The amount and character of the folding can be controlled by adjusting the shape and level of the control signal, allowing the user to create a wide range of timbres and sounds. Wave folding is often used in combination with other synthesis techniques, such as filtering and envelope shaping, to create complex and evolving sounds.

What is Distortion?

Distortion is a type of effect that is used to introduce non-linearities into a signal, resulting in a distorted or overdriven sound. Distortion is often used to add edge or grit to a sound. It can be achieved in a number of ways, including by overdriving an amplifier, reducing the audio sample rate, over-compressing your audio, applying audio rate modulation to your audio signal, or applying a technique like wavefolding.

Distortion is typically controlled by adjusting the amount of overdrive or gain in the signal path, which determines the amount and character of the distortion. Different types of distortion, such as soft-clipping or hard-clipping, can be used to create a wide range of sounds, from subtle overdrive to intense, saturated distortion. Distortion is often used in combination with other effects, such as filtering or delay, to create complex and interesting sounds. It is an important part of many styles of electronic music, where it is used to add character and texture to the synthesized sound.

Compiled by Matthew Piecora (aka EZBOT)