Ambient Eurorack Jam: Modular Synth Walkthrough & Sound Design

Control Voltage (CV) controls module parameters and can be fixed or moving. An LFO sends moving CV for modulation. Gate signals are square waves with only two values (high and zero), commonly used by keyboards to indicate note playing. Trigger signals are fast impulses that quickly rise and fall, used for clock signals in sequencers. The square wave output of an oscillator can serve as a gate signal to trigger modules like drum modules, with frequency controlling trigger rate.

Control Voltage (CV) is the fundamental control mechanism in modular synthesizers where all parameters are controlled by electrical voltage. When voltage is sent to a module, it changes behavior—increasing voltage might increase volume or change pitch. Gate signals determine when sounds are active or inactive, turning sounds on and off for specific durations. Clock division and multiplication allow musicians to create different rhythmic patterns from a single tempo source, such as converting 128 BPM into 256 BPM for faster patterns.

CV (Control Voltage) and Gate are fundamental signal types in modular synthesizers. Gate functions like a light switch, controlling when data is sent out (on/off states). CV functions like a dimmer knob, sending values from 0-127 to control parameter intensity. In early modular systems, users created sounds from scratch using dedicated modules connected via physical cables. In Reason/Record, these concepts translate to routing signals between devices. Gate signals control timing and duration of sound events, while CV signals control parameter values like cutoff frequency, LFO rate, and filter envelope.

In modular synthesizers, control voltage (CV) signals tell modules what to do and how to do it, with a standard 1V per octave characteristic for pitch control; gate signals are binary (+5V/0V) signals that control when audio passes through, functioning like a switch that opens and closes based on key press duration; trigger signals are very short impulses used to initiate processes and synchronize modules; and audio signals are the actual sound waves that travel through the audio path. These signal types can be interchanged and 'mashed up' creatively, as there is no insurmountable border between them in modular synthesis.

This section explains the core concepts of CV and gate signals used in analog and semi-modular synthesizers. CV stands for Control Voltage, an older standard where one volt equals one octave of pitch change. Gates are on/off signals that trigger note playback by activating oscillators and envelope generators. Visual demonstrations show how CV voltages correspond to LED brightness (higher notes = brighter LEDs) and how gates illuminate briefly when notes are pressed. These signals can be routed to modulation inputs on synthesizers to control parameters beyond pitch, such as envelope decay time, creating dynamic, evolving sounds where parameters change automatically during performance.

This video demonstrates how to create instant beats using four Arturia/Korg synthesizers (MicroFreak, Volca Drum, Volca Keys, and Monotron) without a computer. The Arturia MicroFreak serves as the central controller, syncing playback and tempo to the Volca Drum and Volca Keys through patch cables. The Monotron adds unique effects like cutoff filters and delay to the drum sounds. Each synthesizer offers distinct capabilities: the MicroFreak provides bass and synth presets with adjustable filters and oscillators, the Volca Drum generates glitchy percussion from scratch, the Volca Keys creates bass sounds with cutoff and resonance controls, and the Monotron adds experimental textures and effects. This setup allows producers to create crunchy percussion, freaky leads, and lo-fi sweeps directly from the devices.

To sync the Arturia Microfreak with Korg Volcas, set the Microfreak as the master clock by configuring its sync source to 'int' (internal), then connect a 3.5mm cable from the Microfreak's clock out jack to the Volca's sink in jack; since neither device has audio inputs, each must be connected to a separate input on an external mixer or audio interface for recording.

This section explains the complete MIDI architecture for connecting multiple synthesizers. The Arturia KeyStep Pro serves as the central sequencer with 4 tracks of MIDI sequencing, controlling all instruments including the Korg Volca Drum via its built-in drum sequencer. The Roland Boutique series devices enable daisy-chained MIDI connections using their MIDI out as a mini through, eliminating the need for separate MIDI splitters. The KeyStep Pro has two MIDI outs: one to the Volca Drum and another daisy-chained through the SH-01a, SH-02, and JU-06. Clock synchronization between the KeyStep Pro and Korg NTS-1 uses a 3.5mm cable from the KeyStep Pro's clock output to the NTS-1's sync input, ensuring the arpeggiator matches the tempo of other devices.

The Arturia Microfreak can function as a master clock to synchronize multiple electronic music devices including synthesizers, drum machines, and sequencers by routing its clock out and MIDI out signals through a modular system to devices like the Moog Grandmother, Behringer Odyssey, Behringer modular system, and Alesis SR16 drum machine, with a MIDI switcher box allowing selective control over which devices receive the clock signal.

To sync the Arturia Microfreak with the Korg NTS-1, connect the clock output of the Microfreak to the clock input of the NTS-1 using an eighth-inch cable; then press and hold the arpeggiator button on the NTS-1 until it latches, and use the tempo knob to set the BPM, allowing both devices to operate in sync with the same tempo.

In visual programming environments like Plugdata/Pure Data, audio rate objects process signals at the computer's sample rate (determined by buffer size) and are used for real-time audio generation and processing, while control rate objects operate at a slower rate (default 20ms) for handling numerical values and generating control signals; audio objects are distinguished by their tilde (~) symbol and different color coding, and proper signal conversion between rates using objects like float~ is essential to prevent audible artifacts such as clicks when connecting control values to audio processing stages.

Audio signals represent actual sound waves—rapid vibrations of air molecules that our ears perceive as sound. When converting real sounds into recordings, these air vibrations are transformed into patterns of electricity. Control voltage signals, while also represented as electrical voltages, serve a different purpose—they represent slow-moving control information that shapes how audio signals are generated and processed. Both types of signals exist as voltage variations, but they operate on fundamentally different time scales and serve different musical purposes.

Audio signals and control voltage are fundamentally the same type of electrical signal—both are voltage waves. The difference lies in speed: audio waves vibrate extremely fast (creating sound), while CV waves move more slowly. When CV is sent to audio outputs, it produces noise or clicking sounds because the wave is too slow to hear. Conversely, audio can be used as CV by modulating it at the speed of sound.

In modular synthesis, all signals fall into one of two categories: audio signals (which carry sound) and control voltage (CV) signals (which are precise voltages used to modulate parameters of audio or other control voltages). For example, CV from a Maths module can control the pitch of a Braids module, while another CV channel can modulate the speed at which that first channel rises and falls. This dual-signal system enables complex modulation possibilities.

Sound generation in Pure Data relies on oscillator objects (osc~) producing periodic waveforms like sine waves, with the tilde (~) indicating audio-rate processing capability. Volume control is achieved through multiplication objects that scale signal amplitude between -1 and 1. Real-time parameter control uses slider objects (V sliders) whose output ranges can be customized through properties. Frequency control requires mathematical mapping to convert normalized slider values into meaningful frequency ranges. A critical distinction exists between control-rate signals (slow-changing parameters) and audio-rate signals—direct control of audio objects by control-rate signals causes audible clicks due to instantaneous parameter changes, requiring smoothing techniques for smooth transitions.