Week 7 – VCV Rack and Modular Synthesis

1. Fundamental Concepts of Modular Synthesis

VCV Rack is a powerful open-source modular synthesis simulator that allows you to experiment and create sound synthesis patches in a virtual environment. Designed to emulate the behavior of physical modular synthesizers, VCV Rack offers users the ability to build complex sounds by connecting various modules, each with a specific function such as oscillators, filters, effects, and modulation controls. The open-source nature of VCV Rack enables vast expandability and a highly active community that constantly contributes new modules, further expanding its capabilities and making it an extremely versatile tool accessible to everyone, from beginners to sound synthesis experts.

Before starting, you need to create a free account on the VCV Rack website. Download Once you’ve created an account, you can download modules from the official library, many of which are free.

To explore available modules, visit the VCV Rack Module Library.

A modular synthesizer is a system composed of various independent modules, each with a specific function, such as oscillators, filters, amplifiers, and control modules. Unlike traditional synthesizers, which often have a predefined and limited signal flow, a modular synthesizer allows users to create their own signal path by connecting the various modules together with virtual cables, enabling infinite customization of the sound. This approach offers greater creative freedom and a deeper understanding of how the various components interact to generate sound.

In modular synthesis, the term Voltage Control (VC) is crucial. It refers to the ability to control parameters of a module using voltages, which means that one module can control the behavior of another. This is the foundation of what makes modular synthesis so flexible and powerful. For example, a Voltage Controlled Oscillator (VCO) uses incoming voltages to change its pitch.

Control Voltage (CV) is used to describe the signals that control parameters like pitch, filter cutoff, or amplitude. Different modules generate and respond to CVs, allowing you to modulate various aspects of your patch dynamically. Another key term is the Gate, which is a type of signal used to trigger events, such as starting an envelope or triggering a note. Typically, CV represents continuous control, while Gate represents an on/off state, like pressing a key on a keyboard.

Modular synthesis offers numerous advantages over traditional synthesizers, including extreme flexibility in creating and modifying sounds, limitless creativity thanks to the ability to freely combine modules, and total control over every aspect of the generated sound. Each module can be chosen and configured by the user, allowing the construction of unique instruments and sounds never heard before. This approach also allows for an in-depth understanding of the sound synthesis process, ideal for those who wish to delve into the world of sound creation in a detailed and personal way.

2. Basic Patch

A basic patch in a modular synth almost always starts with a series of fundamental modules, which include an oscillator (VCO), a voltage-controlled amplifier (VCA), and a voltage-controlled filter (VCF). The oscillator generates the basic sound, which can be one of the various available waveforms: sine, triangle, sawtooth, or square. Each waveform has a characteristic timbre that can be further manipulated through other modules. After the VCO, the signal is sent to a VCA, which allows dynamic volume control, often in combination with an envelope module to manage the attack, decay, sustain, and release of the sound. Finally, the signal passes through a filter (VCF), which can be used to further sculpt the sound by removing or emphasizing certain frequencies. This chain is common because it provides complete control over the signal and allows for the generation of a wide range of different sounds, from simple to very complex.

To further enrich the patch, it’s always useful to add an LFO (Low-Frequency Oscillator) module to add modulation and movement to the sound, such as varying the frequency of the oscillator or the filter cutoff over time. An Envelope module is also indispensable for controlling the dynamics of the sound, defining how the volume changes over time. Additionally, a Mixer module can be very useful for combining signals from multiple VCOs, thus creating even richer and more complex sounds. Every patch starts with this basic structure because it offers the minimum necessary to explore both the generation and modification of sound. From here, you can add additional modules like effects (reverb, delay) and control modules to make the final result more dynamic and interesting.

3. Overview of the VCV Rack Interface

To begin, open VCV Rack and take a look at the user interface. VCV Rack opens with an empty grid, ready to be filled with modules. The first thing you’ll notice is the main ‘rack,’ which represents the virtual space where you’ll add and organize your modules. At the top, you’ll find the toolbar, which provides access to important functions like saving projects, managing the library, and other configuration options. The module library is located on the right side and allows you to select from a wide range of modules of different types. Learning to navigate these sections is crucial to work efficiently and build successful patches. Once you’ve understood the interface, you can start adding modules and organizing your rack to maximize creative flow.

Main Rack

The main rack represents the empty grid within VCV Rack where you can add and organize modules. It’s similar to the physical case of a modular synthesizer, and it’s here that you place the various modules to create a patch. Each module has a specific function, and how they are connected determines the signal path and the nature of the sound.

Toolbar

The toolbar is located at the top of the interface and contains fundamental options for using the program, such as saving the project, loading previous patches, and managing the library. Other useful tools include the play/pause button, which starts the system’s internal clock, and global settings to configure the program’s preferences.

Shortcuts and Useful Commands

• Add a Module: Press Ctrl+M (or Cmd+M on Mac) to quickly open the module library and search for a module to add to the rack.
• Duplicate Module: Select a module and press Ctrl+D (or Cmd+D on Mac) to duplicate it. This is useful when you want to create a similar configuration without having to reconnect all the cables.
• Delete a Module: Select the module to delete and press the Delete key (or Backspace on Mac).
• Connecting Cables: Hold down the Ctrl key (or Cmd on Mac) while dragging cables to create multiple connections with greater precision.
• Navigate Between Modules: Use the mouse wheel to zoom in or out and better view the modules within the rack. This is useful to maintain a clear vision when the patch becomes more complex.
• Organize Modules: Drag modules while holding down the Shift key to move them more smoothly without accidentally disconnecting cables.
• Save and Load Patches: Press Ctrl+S (or Cmd+S on Mac) to save the current patch. You can load a previous patch with Ctrl+O (or Cmd+O on Mac).

4. Basic Modules

• VCO (Voltage Controlled Oscillator): Introduction to different types of sound waves (sine, saw, square, triangle) and their use.

  VCOs are fundamental modules for sound generation. Each type of wave produces a sound with unique tonal characteristics: the sine wave has a soft and pure sound, the square wave produces tones rich in even harmonics, while the sawtooth wave is ideal for aggressive and full sounds. Connecting the VCO to an output module allows you to directly hear the differences between the various waveforms.

• VCA (Voltage Controlled Amplifier): Explanation of dynamic volume control and its importance.

  The VCA is used to manage the signal level, controlling how much of the sound passes through. It is often used together with an envelope module to create controlled dynamics, such as sounds with a fast attack or long decay, allowing the sound to transform from static to more lively and interesting.

• Filter (VCF – Voltage Controlled Filter): Introduction to low-pass, high-pass, and band-pass filters and how to use them to shape the sound.

  Filters are used to remove or emphasize certain frequencies of the signal. A low-pass filter cuts high frequencies, making the sound darker, while a high-pass filter cuts low frequencies, giving a brighter sound. Filters are essential for sculpting the character of the sound and focusing it in a specific context.

• LFO (Low-Frequency Oscillator): Show how the LFO can add movement and modulation to sounds.

  LFOs are used to modulate parameters of other modules, such as the frequency of the VCO or the cutoff of the filter. For example, connecting an LFO to the frequency of the VCO produces a vibrato effect, creating cyclic and dynamic effects that add interest to the sound.

5. Creating a Basic Patch

Creating a Simple Patch

In this section, we’ll learn how to create a simple patch to understand the signal flow within VCV Rack. Follow these steps to connect the modules and obtain a basic sound:

1. Add an Oscillator (VCO): Start by adding a VCO module to the rack. This module will generate the basic sound.
2. Connect the VCO to a Voltage-Controlled Amplifier (VCA): Connect the output of the VCO to the input of the VCA. This will allow you to control the volume of the sound.
3. Add a Filter (VCF): Add a VCF module to the rack. Connect the output of the VCA to the input of the filter. This will allow you to sculpt the sound by eliminating or emphasizing certain frequencies.
4. Connect the Filter to the Output: Finally, connect the output of the VCF to the rack’s output module to be able to hear the sound through speakers or headphones.
5. Add an Envelope Module (optional): To make the sound more expressive, add an Envelope module and connect it to the VCA. This will allow you to control how the sound’s volume changes over time, defining the attack, decay, sustain, and release.
6. Add an LFO for Modulation: You can add an LFO and connect it to the filter’s cutoff to add movement to the sound. For example, the LFO will vary the filter’s cutoff point over time, creating an interesting modulation effect.

Patching Concept: Think of patching as a metaphor for physical cables connecting the various modules. This will help you better understand the signal flow and how modules interact to produce the sound.

Explore and Experiment: Try modifying the parameters of the VCO, filter, and VCA to see how the sound changes. Add additional modules, such as reverb or delay effects, to make your patch more complex and interesting. Observe how each module affects the overall sound and try to develop your personal understanding of the signal flow.

6. Mindset for Modular Synthesis

Modular synthesis requires a particular mindset, made of curiosity, openness to experimentation, and a certain tolerance for uncertainty. Approaching modular synthesis means being ready to explore sounds in ways that are not always predictable. It’s important to abandon the need for immediate results and let yourself be guided by the process itself. Creativity is the main engine: the idea is not just to create sounds but also to discover new timbral possibilities and experiment.

What Modular Synthesis Allows You to Do

Modular synthesis allows you to build unique instruments from scratch. It’s not just about using presets but understanding every single component that participates in creating the sound. This approach allows for a deep understanding of the sound and its behavior, as well as the freedom to combine modules creatively to achieve results that would not be possible with standard instruments.

Common Difficulties

One of the main obstacles is the steep learning curve. Modular synthesis requires knowledge of various technical concepts and a good understanding of the signal flow. It’s easy to feel overwhelmed at first by the complexity of the modules and the infinite number of possible connections.

Advantages

Modular synthesis offers unparalleled flexibility. You have the possibility to create complex and dynamic sounds with total control over the parameters, something that is often not possible with standard synthesizers. Additionally, it allows you to discover your own sonic style, as each patch is a unique process that reflects the user’s choices and creativity.

Common Problems and Solutions

• Problem: Initial confusion in understanding where to start and which modules to use.

  Solution: Start with a simple basic structure and add one module at a time, experimenting with its effect. Keeping the project simple at the beginning helps to better understand the role of each component.

• Problem: Managing the chaos of too many connections.

  Solution: Learn to visually organize the rack and use different colors for the cables (when possible) to keep the signal flow clear. Dividing the patch into logical sections (generation, modulation, effects) greatly helps in understanding.

• Problem: Lack of immediacy compared to traditional synthesizers.

  Solution: Embrace the process as part of the fun. Modular synthesis is as much an experience of learning as it is of musical creation; every small step forward is a discovery that increases your understanding.

7. Polyphony in VCV Rack

Polyphony in VCV Rack is a feature that allows you to play multiple notes simultaneously, making patches richer and more complex. In a modular synthesizer, achieving polyphony requires the use of multiple CV (Control Voltage) connections to control different oscillators or other modules simultaneously. Here’s how to achieve polyphony in VCV Rack:

1. Polyphonic Modules: Some modules in VCV Rack directly support polyphony. For example, many VCO, VCF, and VCA modules have polyphonic inputs and outputs that can handle multiple CV channels in a single cable. You can verify if a module is polyphonic by checking if its connectors are highlighted with a colored border.
2. Using MIDI-CV for Polyphony: To start, add a MIDI-CV module and configure your MIDI controller. In the module’s panel, increase the number of voices to enable polyphony. This module will transform MIDI messages into control signals that can handle multiple notes simultaneously, sending CV for pitch, gate, and velocity to subsequent modules.
3. Polyphonic Connections: When a polyphonic cable is used in VCV Rack, it carries multiple data channels simultaneously. For example, you can connect the polyphonic CV output of a MIDI-CV module to the input of a polyphonic VCO module. In this way, each voice from the MIDI controller is handled by a separate instance of the VCO, creating real polyphony.
4. Splitting and Managing Polyphonic Signals: You can use modules like Poly Split and Poly Merge to split and combine polyphonic signals. For example, if you want to apply different effects to each voice of your polyphonic patch, you can use a Poly Split to separate each channel and then process each signal individually, eventually recombining them with a Poly Merge.
5. Applying Polyphonic Modulations: Another important aspect of polyphony is the application of modulations. You can use a polyphonic LFO to modulate different parameters of each voice independently, creating more complex timbral variations. Ensure that the LFO module supports polyphony and connect the polyphonic LFO output to the desired parameters.
6. Using the Polyphonic VCA: To manage the volume of each voice separately, you can use a polyphonic VCA. Connect the output of the polyphonic VCO to the input of the polyphonic VCA, and control the VCA with a polyphonic Envelope module to give dynamics to each played note.

This configuration allows you to explore all the potential of polyphony, making your patches much more expressive and interesting. With polyphony, VCV Rack becomes a powerful tool for creating complex textures and harmonizations that would be difficult to achieve with a monophonic configuration.

8. FM, AM Synthesis, and Ring Modulator

Modular synthesis offers multiple techniques to create complex and articulated sounds. Among these, frequency modulation (FM), amplitude modulation (AM), and the use of the Ring Modulator are among the most important. Let’s see how they work and the main differences between them.

Frequency Modulation (FM)

FM synthesis is a technique where the frequency of one oscillator (carrier) is modulated by another oscillator (modulator). This process generates rich and complex harmonics, which can give rise to metallic or organic sounds. In an FM patch, a VCO is used to directly modulate the frequency of another VCO. The speed and depth of the modulation determine the complexity of the resulting sound. This technique is particularly useful for creating dynamic sounds like bells, metallic basses, and evolving textures.

Amplitude Modulation (AM)

Amplitude modulation (AM) involves modulating the volume of a signal (carrier) using another signal (modulator). In other words, the modulator signal controls the amplitude of the carrier signal, creating volume variations that can produce interesting sound effects, often with a pulsing or trembling character. AM synthesis is useful for adding movement and dynamics to a sound but generates fewer harmonics than FM, often resulting in a simpler but very expressive sound.

Ring Modulator

The Ring Modulator is a module used to combine two audio signals, generating a result that contains the sums and differences of the original signals’ frequencies. This process creates often metallic or inharmonic sounds, characterized by a unique timbral quality. Unlike AM modulation, the Ring Modulator does not retain the original frequencies of the signals but produces new inharmonic components, ideal for creating atonal or percussive textures.

Difference Between LFO and FM/AM/Ring Modulator

An LFO (Low-Frequency Oscillator) is mainly used to modulate parameters of other modules at low frequencies, creating effects like vibrato, tremolo, or slow and cyclical variations. LFOs operate at much lower frequencies than the oscillators used in FM or AM and are often employed to modulate the cutoff of a filter or the volume of a VCA without generating new harmonics.

Conversely, FM and AM use higher frequencies to modulate signals, adding harmonic complexity and creating entirely new sounds. The Ring Modulator, on the other hand, distinguishes itself by multiplying two signals together, generating frequencies that were not present in the original signals, often with a particularly inharmonic and rich texture result.

These modulation techniques are fundamental to understanding how modular synthesis allows the creation of complex and interesting sounds, expanding the sonic possibilities available to the musician. Experimenting with FM, AM, and the Ring Modulator allows you to explore new sonic territories and develop a unique creative language.

9. Creation of a Rhythmic Patch

• Using the Sequencer Module: Utilize the Sequencer module to create a rhythmic sequence.
• Introduction to the Clock Module: The Clock module synchronizes various components.
• Add a Noise Module and an Envelope Module: Create a simple drum pattern by combining noise with an envelope to shape percussive sounds.
• Building the Rhythmic Pattern: Use the sequencer to trigger different modules based on the timing set by the clock module, creating interesting and varied rhythmic patterns. The Noise module can simulate percussion sounds, while the envelope controls the duration of each sound.

10. Modulation and Creative Effects

• Advanced Modulation: Add advanced modulation using the LFO to modulate the VCO’s frequency or the filter’s cutoff.
• Introduction to Delay or Reverb Modules: Add depth and spatiality to the sound.
• Create Atmospheric Sounds: Build an example of a “spacey” or atmospheric sound by combining VCO, VCF, and LFO with effects.
• Using Effects: Use the Delay module to create echoes that repeat over time, adding depth to the sound. The Reverb module can create a larger environment, like a room or a cavern, making the sound more immersive.

11. Individual Project: Personal Patch

Guide for the Individual Project with Examples of Patches and Details of Each Step

Step 1: Choosing the Basic Modules

Identify Necessary Modules: Each student should identify the modules needed for their patch. For a basic patch, it’s recommended to use at least one oscillator (VCO), one amplifier (VCA), one filter (VCF), and one Envelope module.

Define Your Goal: Decide what you want to achieve with your patch: a bass sound, an atmospheric texture, or a rhythmic pattern? This will guide your module selection.

Step 2: Connecting the Modules

Create the Signal Chain: Once you’ve chosen the modules, connect the cables to create the signal flow. For example, starting from the VCO, connect the signal to the VCA for volume control and then to the VCF to shape the sound. Understanding how signals travel between modules is crucial to achieving the desired result.

Envelope and VCA: Connect an Envelope to the VCA to add dynamics to the sound, such as controlling the attack and release. This step is essential to make the sound more natural and dynamic.

Step 3: Adding Modulation

Use the LFO: Add an LFO (Low-Frequency Oscillator) to modulate one of the parameters, such as the VCO’s frequency or the filter’s cutoff. This helps add movement to the sound, creating tremolo effects, vibrato, or timbral variations.

Sample & Hold and Random Modulation (Advanced Level): For advanced users, try adding a Sample & Hold module to create random modulation effects. This can be used to create unpredictable variations and complex textures.

Step 4: Applying Effects

Delay and Reverb: To give more depth to the sound, apply Delay and Reverb effects. For example, you can connect the VCF to a Delay module to get a repeated echo or use a Reverb to create a spatial environment around the sound.

Creative Routing: For more experienced users, you can experiment with chained effects, such as using multiple Delay or Reverb modules in series or parallel to create complex and layered effects.

Step 5: Using the Sequencer

Creating Rhythmic Patterns: Use a Sequencer to create a sequence of notes or rhythmic patterns. This can be synchronized with a Clock to ensure the rhythm remains consistent. For advanced patches, the Sequencer can be used to control multiple modules simultaneously, creating complex interactions.

Interaction Between Sequencer and Other Modules: Connect the Sequencer to modules like VCOs and VCFs to automate changes in pitch and timbre. More advanced students can use multiple sequencers to modulate different parameters simultaneously, creating intricate variations.

Step 6: Testing and Experimenting

Sonic Exploration: Now that the patch has been assembled, experiment with the various parameters. Modify the filter’s cutoff, change the VCO’s waveform, or adjust the Delay’s time. The goal is to explore all possibilities and understand how each module contributes to the final sound.

Problem Solving: If something doesn’t sound as expected, trace the signal path to find any connection errors. This is an excellent exercise to improve understanding of the signal flow.

Step 7: Sharing and Review

Presenting the Patch: Each student will present their patch to the class. Explain your module choices, how you created the signal flow, and how the different modules interact. This not only helps develop communication skills but also allows you to receive feedback and suggestions from classmates and the instructor.

Peer-to-Peer Feedback: More experienced students can offer advice on advanced techniques, such as using cross-modulation or adding logic modules for unconventional effects.

Examples of Patches

Basic Patch (Beginner Level)

1. Modules to Use: VCO, VCA, VCF, LFO, Envelope
2. Description:
   • VCO: Generates the basic sound. Use a simple waveform like a sine wave.
   • VCA: Connect the VCO to the VCA to control the volume.
   • Envelope: Connect the envelope to the VCA to add dynamics to the sound (e.g., soft attack and short release).
   • VCF: Use the filter to shape the sound, for example by applying a low-pass filter.
   • LFO: Add an LFO to modulate the filter’s cutoff frequency, creating a cyclical movement in the sound.

Intermediate Patch (Intermediate Level)

1. Modules to Use: 2x VCO, VCA, Mixer, VCF, LFO, Sequencer
2. Description:
   • VCO 1 and VCO 2: Use two oscillators with different waveforms (e.g., sawtooth and square) to generate richer sounds.
   • Mixer: Connect both VCOs to a Mixer to combine the signals.
   • VCA: Pass the signal from the Mixer to the VCA for volume control.
   • VCF: Connect the VCA output to the filter to shape the sound (you can experiment with a band-pass filter for a more selective effect).
   • LFO: Use an LFO to modulate the VCO’s frequency or the filter’s cutoff to add further movement.
   • Sequencer: Add a Sequencer to create a simple melody line, synchronizing everything with a clock.

Advanced Patch (Expert Level)

1. Modules to Use: 3x VCO, Ring Modulator, Noise Generator, VCA, VCF, Sample & Hold, Delay, Reverb, Sequencer
2. Description:
   • VCO 1, VCO 2, VCO 3: Use three oscillators. One can act as a modulator in an FM (Frequency Modulation) configuration to create complex and articulated sounds.
   • Ring Modulator: Connect two of the VCOs to the Ring Modulator to obtain metallic and inharmonic sounds.
   • Noise Generator: Add a noise generator for percussive effects or sound textures.
   • VCF: Pass the combined signal from the VCOs and Ring Modulator through a multimode filter to experiment with timbral variations.
   • Sample & Hold: Use the Sample & Hold module to generate random changes in the sound, modulating, for example, the filter’s frequency or the VCO’s pitch.
   • Delay and Reverb: Add Delay and Reverb to give space and depth to the sound, creating a more immersive environment.
   • Sequencer: Use an advanced Sequencer to create complex melodic and rhythmic sequences, possibly synchronizing with external modules.