Patching Techniques

Patching is how you "play" a modular synthesizer: every cable decides where a sound or a control signal goes. This guide explains the two classic schools of synthesis – East Coast and West Coast – and the basic patches every modular player uses. The diagrams are simplified examples; your modules may be labelled differently.

New to modular? Start with Getting Started with Modular Synthesizers. You'll need some patch cables.

East Coast: subtractive synthesis

Named after Robert Moog's work on the US East Coast. You start with a harmonically rich waveform (saw or square) and remove frequencies with a filter. An envelope opens the filter and the VCA for each note.

1. Sequencer or keyboard pitch CV → VCO 1V/oct input.
2. VCO saw output → VCF input.
3. VCF output → VCA input → your mixer or speakers.
4. Sequencer gate → envelope gate input.
5. Envelope → VCA CV (the note's volume shape) and, via an attenuator, → VCF cutoff (the note's brightness).

Sounds like: fat basses, classic leads, squelchy acid lines.

West Coast: additive, FM and waveshaping

Named after Don Buchla's work in California. You start with a simple waveform (sine or triangle) and add harmonics with frequency modulation and a wavefolder. Instead of a VCF + VCA, a low-pass gate (often using a vactrol) closes volume and brightness together, giving a natural, plucked or struck sound.

1. Modulation oscillator → FM input of the complex (principal) oscillator.
2. Principal oscillator (sine/triangle) → wavefolder → low-pass gate.
3. A trigger → function generator (a simple attack/decay envelope).
4. Function generator → low-pass gate CV, and also → wavefolder amount, so each note opens up bright and decays darker.

Sounds like: bell-like plucks, woody percussion, evolving metallic tones. Typical modules: complex oscillators, wavefolders, low-pass gates and function generators.

The difference you can hear

East Coast takes away: a bright saw gets darker through the filter. West Coast adds: a pure sine gets brighter as the wavefolder folds its peaks back on themselves, creating new harmonics.

You don't have to choose: most modern Eurorack systems mix both, for example a wavefolder after a filter, or FM between two "East Coast" oscillators.

1. Vibrato and tremolo (LFO modulation)

An LFO is a slow oscillator used to move other parameters.

• Vibrato: LFO → VCO pitch/FM input. Keep the amount small (use an attenuator), or the pitch will wobble wildly.
• Tremolo: LFO → VCA CV input for a pulsing volume.
• Try the LFO on the filter cutoff for a slow sweep, or on pulse width (PWM) for a chorus-like shimmer.

2. FM: frequency modulation

Patch one oscillator (the modulator) into the FM input of another (the carrier). At audio rate this creates new harmonics instead of vibrato.

• Ratio between the two pitches decides the character: simple ratios (1:1, 2:1) sound harmonic, odd ratios sound metallic or bell-like.
• Depth (the attenuator or FM knob) decides brightness. Modulate the depth with an envelope for evolving tones.
• Linear FM stays in tune when you change depth; exponential FM drifts in pitch but sounds wilder.

3. Random melodies with sample & hold

A sample & hold grabs the voltage at its input every time it receives a clock pulse, and holds it until the next one. Feed it noise and you get a new random voltage on every step.

1. Noise → S&H input.
2. Clock → S&H trigger input.
3. S&H output → quantizer, which snaps the random voltages to a musical scale.
4. Quantizer → VCO pitch. Instant generative melody!

4. Pinging a filter (instant percussion)

Turn a filter's resonance up until it nearly self-oscillates, then send it a short trigger instead of audio. The filter "rings" like a struck drum or wood block. Set the pitch with the cutoff knob and the decay with resonance.

The same trick works with a low-pass gate: a trigger "pings" the vactrol for a natural pluck – the heart of many West Coast patches.

5. Clocks and clock division

One master clock keeps everything in time. A clock divider turns it into slower, related rhythms: ÷2 plays every second pulse, ÷4 every fourth, and so on.

• Clock ÷1 → hi-hat, ÷2 → snare, ÷4 → kick: a basic beat.
• Feed different divisions to several sequencers or envelopes for polyrhythms.
• Try odd divisions (÷3, ÷5, ÷7) for patterns that drift against each other.

6. Scaling CV: attenuverters and offsets

Control voltages often need adjusting before they do what you want:

• An attenuator makes a CV smaller (less modulation).
• An attenuverter can also flip it upside down, so a rising envelope closes a filter instead of opening it.
• An offset adds a fixed voltage, moving the whole range up or down – for example to keep an LFO in the positive range for a VCA.

Precision adders and mixers with these controls are some of the most useful utility modules you can own.

7. Self-patching: a cycling envelope

Many envelopes and function generators have an end-of-cycle (EOC) output that fires a trigger when the envelope finishes. Patch EOC back into the envelope's own trigger input and it restarts forever: your envelope becomes an LFO whose shape you set with the attack and decay knobs.

Feedback patches like this – and modules modulating each other in loops – are the basis of generative, self-playing patches.