UNSTABLE Synthesizer — Owner's Manual

User Manual

Expressive · Emotional · Evocative.

Inspired by the pinnacle of analog synthesizers, UNSTABLE takes on the legendary Yamaha CS-80 — and gets closer to the real hardware than anything else out there. Soulful, organic, and with a mind of its own, it captures the eccentricities, instabilities and vibe of the original that inspired an entire generation through artists like Vangelis, Jean-Michel Jarre, Michael Jackson, Toto, and many more.

INSTALLATION

Download the latest version of UNSTABLE from the product page. Extract the ZIP archive and copy the plugin file to the appropriate folder for your system:

Mac

VST3: /Library/Audio/Plug-Ins/VST3/
AU: /Library/Audio/Plug-Ins/Components/

PC

VST3: C:\Program Files\Common Files\VST3\

After copying the files, rescan your plugins in your DAW (most DAWs do this automatically on startup).

Mac users: You may need to approve the use of unsigned software in your system settings before the plugin will load. See the Apple guide or this YouTube tutorial for instructions.

LICENSING & REGISTRATION

UNSTABLE runs as a fully functional 10-minute trial per session — no features are removed and no watermarks are applied. After 10 minutes the plugin will ask to be registered. You can restart your DAW to begin another trial session at any time.

To unlock unlimited use, purchase a license code from Patreon or Gumroad, then enter the code in the registration dialog that appears when the trial expires. Once registered, the plugin is unlocked permanently on your machine.

Visit the UNSTABLE product page for current pricing and download links.

GENERAL OVERVIEW

UNSTABLE features two independent synthesis layers, namely CHANNEL I and II (pink and purple) which can be mixed using the MIX slider on the bottom right to create a richer sound. The synth engine provides 64 voices of polyphony shared across both layers — effectively 32 notes, as both channels are always active. Each layer is clocked independently, ensuring the oscillators, even if set to the exact same values, are ever so slightly off sync. This is by design and cannot be undone. The CHANNEL II DETUNE slider lets you tune channel II away from channel I, from subtle detuning for thickness and beating through to wider intervals for richer, more spread-out layers.

The MAIN SECTION (bottom, blue) is used to apply modification to both or either channel.

The FOOTER SECTION of the plugin allows you to access EFFECT and ARPEGGIATOR controls, the PRESET BROWSER via the corresponding TABS, as well as toggling the RING MODULATOR, ARPEGGIATOR and COMPRESSOR on and off.

GUI SCALING

The UNSTABLE interface is 1580 × 900 pixels at 100% scaling. The GUI can be resized from 50% to 200% to suit your screen resolution and workflow. Right-click anywhere on the plugin background to access the scaling options. A minimum screen resolution of 1920 × 1080 is recommended at 100%.

OSCILLATOR SECTION

Each synthesis channel features an accurately modeled analog OSCILLATOR section with SQUAREWAVE, SAWTOOTH, and NOISE oscillators, all of which can be dialed in from zero to maximum volume. Layer them in any combination — a touch of square under a dominant saw, a hint of noise for breath, or all three together for a complex unified tone. A separate pure SINE oscillator sits after the filter section (see SINE OSCILLATOR below).

PULSE WIDTH

The pulse width dial enables you to select the pulse width of the SQUAREWAVE oscillator from roughly 1% on both sides to 50% at middle position.

PWM / SPEED

By dialing in PWM (Pulse Width Modulation) you apply an automatic back and forth change over time to the pulse width, just like an LFO. PWM selects the strength (wideness) of the modulation, whereas SPEED is the speed of the modulation.

FEET

Each channel has an organ-style footage selector that sets the basic pitch range of the oscillator:

16' — one octave below the played key (bass and sub registers)
8' — concert pitch, the played key sounds at its written pitch
5 1/3' — a perfect fifth above the played key
4' — one octave above the played key
2 2/3' — a perfect fifth above 4'
2' — two octaves above the played key

Because the two channels are independent, you can stack them at different footages for classic organ-style fifths and octave doublings.

FILTER SECTION

Each channel has its own filter section with two filters in series: a resonant high-pass (HPF) followed by a resonant low-pass (LPF). Together they can shape almost any tonal contour, from deep sub-bass through to thin formant peaks.

HPF / RES

The HPF removes harmonics below its cutoff frequency, thinning the sound and removing mud. RES controls resonance at the cutoff — emphasising the frequencies right at the corner.

LPF / RES

The LPF removes harmonics above its cutoff frequency. This is the main brightness control. RES emphasises the frequencies at the cutoff; at higher settings the filter starts to sing, and at the extremes will self-oscillate.

FILTER ENVELOPE

This is the famous Yamaha CS-80 filter envelope, modelled after the original IG00152 master-board envelope generator. Five stages — IL · AL · A · D · R — shape the cutoffs of both filters around the static positions set by the HPF and LPF knobs. The cutoffs can dip below those settings at note start, rise above them during the attack, and decay back down to them while the key is held. The HPF and LPF knobs themselves act as the implicit sustain levels (the envelope's effect on the HPF is half as strong as on the LPF).

IL (Initial Level) — how much the envelope dips below the HPF and LPF settings at note start. At zero there is no dip and the envelope starts right at the knob positions; at maximum the LPF closes down to its minimum and the HPF dips to half its setting.
AL (Attack Level) — how much the envelope rises above the HPF and LPF settings at the peak of the attack. At zero there is no opening sweep; at maximum the filters open fully on every note.
A (Attack) — time from the initial level (IL) up to the attack peak (AL).
D (Decay) — time for the envelope to fall from the attack peak back down to the HPF and LPF settings.
R (Release) — time for the envelope to fall back to its starting position (set by IL) after the key is released.

SINE OSCILLATOR

Each channel has a separate sine oscillator that sits after the filter section. A sine wave has no harmonics, so there is nothing for a filter to shape — placing it after the filter keeps it clean no matter where you set the cutoff. This is where the famous CS-80 bell sounds come from: drop the VCO levels, raise the SINE, and you have a pure, ringing bell tone.

The SINE slider sets its level.

AMP SECTION

Each channel's amplifier carries a full ADSR envelope along with output level and velocity sensitivity.

A (Attack) — the time from key press to full volume.
D (Decay) — the time from peak to the sustain level.
S (Sustain) — the level the note holds at while the key is down.
R (Release) — the time from key release back to silence.
Level — the channel output level.

TOUCH RESPONSE

UNSTABLE responds to three forms of touch from your keyboard: velocity, key position, and aftertouch. Each has its own depth control on the channel it affects.

VELOCITY RESPONSE

The RESPONSE panel of each channel has two velocity controls:

VEL — velocity sensitivity of the amplifier. Sets how much keyboard velocity affects the output level.
VCF — velocity sensitivity of the filter. Sets how much keyboard velocity affects the filter cutoff.

At zero, velocity is ignored and every note plays at the same level and brightness. At maximum, every nuance of your playing comes through.

KEY RESPONSE

KEY sets the keyboard tracking amount of the VCF cutoff. At the middle position the cutoff stays even across the keyboard. Turning KEY up raises the cutoff as you play higher notes; turning it down lowers the cutoff on higher notes.

AFTERTOUCH RESPONSE

AFT controls how much keyboard pressure opens the filter. With a polyphonic-aftertouch controller, pressing harder into a single key opens the filter under your fingers for that note only — hold a chord, lean into one note, and only that voice swells open.

LFO

A low-frequency oscillator generates slow cyclical modulation. Each channel has its own shape, and the two LFOs share a common speed. You then dial in how much LFO is sent to each destination:

LFO → VCO — pitch modulation (vibrato).
LFO → VCF — filter cutoff modulation (filter wobble, growl).

TUNING

These controls live in the MAIN SECTION and apply to both channels.

Initial Bend — a static pitch offset applied at every note start.
Coarse — semitone tuning.
Fine — cents tuning, for subtle detune.
CHANNEL II Detune — detunes channel II against channel I.
Voice Drift — per-voice random tuning drift. Push this for the wandering, never-quite-in-tune analog character that the synthesizer is named for.

PERFORMANCE

UNSTABLE responds to standard performance MIDI from your controller:

Pitch Bend — the pitch bend wheel on your controller. Range fixed at +/- 2 semitones.
Ribbon — a continuous on-screen pitch element.
Aftertouch — polyphonic per-voice pressure (see TOUCH RESPONSE above).
Sustain Pedal — a connected sustain pedal.

EFFECTS

The EFFECTS section hosts three independent effect modules. Additionally the famous RING MODULATOR, an ARPEGGIATOR and COMPRESSOR can be added via a dedicated on/off button in the footer for quick toggling during performance.

RING MODULATOR

A polyphonic ring modulator with its own envelope.

Speed — frequency of the modulating oscillator.
Depth — amount of ring modulation in the output.
Mod — pitch sweep depth on the modulating oscillator.
Attack / Decay — envelope shaping the ring mod amount over each note.

CHORUS

Delay — chorus delay time.
Frequency — modulation rate.
Mod Amount — modulation depth.
Drive — saturation amount inside the chorus path.
High Cut / Low Cut — bandwidth shaping for the chorused signal.

DRIVE

Drive — amount of analog circuit drive applied to the master bus. Drive models the smooth, weighted saturation character of a pushed analogue console bus or a gently driven transformer stage.

COMPRESSOR

A master-bus compressor for evening out dynamics.

DELAY

Time — delay time.
Feedback — repeat amount.
Modulation — modulation of the delay time, for chorused or pitch-warbled repeats.
Size — spatial size of the delay reflections.
Damping — high-frequency absorption in the repeats.
Diffusion — density of the delay reflections.

REVERB

Decay — length of the reverb tail.
Sparkle — adds an octave-up shimmer to the tail.
Sparkle Drift — slow detune of the shimmer.
Drive — saturation inside the reverb path.
High Gain — tonal balance of the tail.
Low Cut — removes lows from the reverb signal.

ARPEGGIATOR

An integrated arpeggiator turns held chords into rhythmic patterns, tempo-synced to your DAW.

Tempo — note division, from whole notes down to 1/32, including dotted and triplet values.
Type — direction or pattern (up, down, alternating, random, programmed).
Shuffle — swing timing.
Steps — number of steps in the pattern, up to 16.
Octave Range — extends the pattern across additional octaves.
Tie — joins consecutive notes into a single sustained note.
Sort — sorts the held chord into pitch order before arpeggiating.
Hold — latches the held chord.
Per-step packs — three programmable rows set semitone offset, velocity, and note length for each step individually.

Dedicated Arpeggiator Pitch and Arpeggiator Expression sections provide further per-step shaping.

PRESETS

Use the PRESET tab in the footer to browse the factory sound library and to save and organise your own sounds. The Init preset under Leads is the clean starting point for sound design from scratch.

For downloads, licensing, audio demos, and factory presets visit the product page:

UNSTABLE Product Page

UNSTABLE Polyphonic Synthesizer User Manual