Voice Architecture
How ESQ-1 Makes Sound
The ESQ-1’s architecture is a big part of why it remains so interesting. It isn’t simply an analog synth with digital oscillators, and it isn’t simply a digital synth with an analog-style filter. It’s a hybrid instrument where digital waves provide the raw character, DCA stages shape the oscillator mix, the filter focuses the tone, and envelopes and modulation bring the sound to life.
Cherry Audio’s version expands that original structure with two independent layers, multiple filter modes, a modern Mod Matrix, Macro controls, Motion tools, MPE support, and per-layer/global effects. The result is still recognizably ESQ-1, but with a much wider modern workflow.
The Basic Signal Path
Each ESQ-1 voice begins with three Digital Wave Oscillators: OSC 1, OSC 2, and OSC 3.
Each oscillator plays one of the original ESQ-1 digital waveforms, then passes through its own DCA before entering the filter:
OSC 1 → DCA 1
OSC 2 → DCA 2
OSC 3 → DCA 3
These three DCA stages control the individual oscillator levels before the signals are combined. From there, the mixed oscillator signal passes through:
Filter → DCA 4 → Effects
That’s the core architecture. The oscillators provide the raw digital tone. DCA 1, DCA 2, and DCA 3 determine how much of each oscillator reaches the filter. The filter shapes the combined tone. DCA 4 controls the final voice level. ENV 4 is closely tied to DCA 4 and is typically used as the main volume envelope.
Why the DCA Stages Matter
The ESQ-1’s DCA structure is more important than it may first appear. DCA 1, DCA 2, and DCA 3 are not simply volume controls after the sound is finished. They shape the oscillator mix before the filter.
That means the harmonic material entering the filter can change over time. One oscillator can provide the body of the sound, another can add a bright attack, and another can fade in as a texture. When those DCA levels are modulated, the sound evolves from the inside, before the filter even begins shaping it.
Tip: Think of DCA 1, DCA 2, and DCA 3 as a programmable oscillator mixer. The filter doesn’t have to process a static blend. It can receive a changing mixture of digital waves.
The Filter and Final Amplifier
After the three oscillator signals are combined, they pass through the Filter. The filter shapes the brightness, focus, and harmonic balance of the sound. One of the most acclaimed features of the original ESQ-1 was its 4-pole 24 dB/octave resonant low-pass analog filter, which was built using the renowned CEM 3379 chip by Curtis Electromusic.
Cherry Audio’s ESQ-1 expands the original concept with four filter modes: Lowpass 12, Lowpass 24, Highpass, and Bandpass.
After the filter, the signal reaches DCA 4, the final amplifier stage. This is where the complete filtered voice gets its final loudness shape. ENV 4 is closely associated with DCA 4, making it central to whether a sound behaves like a pluck, pad, bass, lead, swell, or sustained texture.
Tip: DCA 1, DCA 2, and DCA 3 control the oscillator ingredients. DCA 4 controls the finished voice.
Modulation Gives the Architecture Behavior
The signal path explains where the sound travels. Modulation explains how it moves.
A modulation source, such as an envelope, LFO, velocity, pressure, Macro, pedal, sequencer source, or MPE gesture, can be routed to a destination such as oscillator pitch, oscillator level, filter cutoff, amplifier level, effects parameters, or other available targets.
This is where the ESQ-1 becomes more than a fixed signal path. The oscillators can change pitch. The DCA levels can shift over time. The filter can open, close, pulse, or respond to velocity. A Macro can control the depth of a modulation routing. MPE gestures can add per-note expression when used with a compatible controller.
Tip: The architecture gives ESQ-1 its sound path. Modulation gives it behavior.
Two Complete Layers
Cherry Audio’s ESQ-1 makes this architecture even more powerful by giving each preset two fully independent layers: Layer 1 and Layer 2. Each layer has its own ESQ-1-style synth engine, including oscillators, DCAs, filter, envelopes, modulation, voice behavior, Motion settings, and effects. The layers can be used as one focused sound, stacked together in Layer mode, or split across the keyboard using Split 1 or Split 2.
This means a preset can behave like one instrument, two layered instruments, or a split performance setup. One layer might provide a warm pad while the other adds a bright digital attack. One layer might hold a sustained texture while the other runs a sequence. One layer might use a lowpass filter for body while the other uses highpass or bandpass for air, edge, or vocal-like color.
Tip: When a patch sounds complex, solo each layer. You’ll often discover that one layer provides the body while the other adds motion, attack, width, or atmosphere.
Effects Routing
After the synth engine, ESQ-1’s sound reaches the effects section. Cherry Audio’s ESQ-1 includes separate effects chains for Layer 1 and Layer 2, plus a Global effects chain that processes both layers together. The routing is:
Layer 1 synth engine → Layer 1 effects → Global effects
Layer 2 synth engine → Layer 2 effects → Global effects
This lets each layer have its own processing while still sharing final effects for glue, space, and polish. For example, Layer 1 might use chorus and delay for a wide digital pad, while Layer 2 uses distortion or compression for a more focused attack. Both layers can then pass through the same Global reverb to place them in a shared space.
The Big Picture
Once you understand the ESQ-1 architecture, the instrument becomes much easier to program:
Choose the raw digital waveforms with OSC 1, OSC 2, and OSC 3.
Set their pre-filter levels with DCA 1, DCA 2, and DCA 3.
Shape the combined tone with the Filter.
Use DCA 4 and ENV 4 to define the final volume shape.
Use envelopes, LFOs, Macros, Motion, and MPE to add movement and expression.
Use layers and effects to build larger, more polished sounds.
The ESQ-1 isn’t complicated for the sake of being complicated. It simply gives you several meaningful places to shape the sound: at the waveform, oscillator level, filter, amplifier, modulation, layer, and effects stages. Follow the signal path, and the instrument starts to make sense very quickly.