SPC Plugins

ArcSyn v4.0.3 User Manual

ArcSyn Synthesizer Audio Plugin



If you have any problems with installation, authorisation or any other aspect of ArcSyn, please contact us.

PC (32 bit): extract the ArcSyn VST.zip file (Right click, ‘Extract All’), then run the installer. The default installation directory is C:\Program Files (x86)\Steinberg\Vstplugins but you can select whatever location you want. ArcSyn's programs are installed to: C:\Users\*YOU*\Documents\ArcSyn Note: Please do not move ArcSyn's program folder or it will not be able to load any programs.

PC (64 bit): extract the ArcSyn VST.zip file (Right click, ‘Extract All’), then run the installer. The default installation directory is C:\Program Files\Steinberg\Vstplugins but you can select whatever location you want. ArcSyn's programs are installed to: C:\Users\*YOU*\Documents\ArcSyn Note: Please do not move ArcSyn's program folder or it will not be able to load any programs.

Mac: double-click the ArcSyn.pkg file to run the installer, and follow the instructions. By default, all three versions (AudioUnit, VST, and VST3) will be installed, but you can choose which ones you want by unchecking the check boxes. The default plug-in destination folders are Macintosh HD/Library/Audio/Plug-Ins/Components, Macintosh HD/Library/Audio/Plug-Ins/VST, and Macintosh HD/Library/Audio/Plug-Ins/VST3 Note: Please do not move ArcSyn's program folder or ArcSyn will not be able to load or save programs.

Info Screen

When first opened, ArcSyn will display a screen containing three options:


After purchasing an authorisation code from us, enter your name and code into the ArcSyn info window by copying and pasting or typing, then click enter. The name and code are both case-sensitive and you should include any spaces. If you have any difficulty, for instance due to your DAW / sequencer host application ‘stealing’ keypresses and not sending them to the plugin ("Reaper" steals the spacebar, for instance), then look for an option to "send all keyboard input to the plugin", or similar. If you still have problems, please contact us.

What Is It?

ArcSyn is a synthesizer instrument plug-in based on typical analogue synthesizer architecture, i.e., a “virtual analogue” synthesizer. Unlike many virtual analogues, it doesn't try and emulate a specific hardware synthesizer, nor does it use 90% of your computer's CPU time to emulate a filter which can be cloned on a 2" (5 cm) square PCB with $5 worth of components :-) Instead, it takes the "road less well travelled" and explores some unusual avenues of analogue (and digital) synthesis—the sort of capabilities you might find on a well-stocked modular synthesizer, including: unusual waveforms, dividers, logic functions, frequency shifters, and so on. ArcSyn also introduces the concept of LFO wave sequencing, allowing extremely complex modulation patterns.

ArcSyn is laid out approximately like a MiniMoog, so it shouldn't be too difficult to start editing programs and creating interesting sounds, although if you take the time to work out how the LFOs and modulation matrix operate, you'll be able to create much more complex programs. There's also a RANDOM button which you can click at any time if you want some instant (not necessarily musical!) inspiration.

Local Manual

There is a local copy of this manual, to avoid the need for an Internet connection, installed inside the ArcSyn programs folder. In Windows it can be accessed from a link under the ArcSyn entry in the start menu. Note: the most up-to-date version of the manual will always be here online.

Basic Operation

How to resize the GUI

How to select programs

ArcSyn Synthesizer Program Select Display

How to save programs

ArcSyn Synthesizer Save Button

How to manage programs

How to edit programs

How to operate the controls


ArcSyn Synthesizer Undo Button

Undoes the last parameter change. Selecting a new program, or clicking the INIT or RANDOM buttons, will clear the UNDO buffer. An umlimited number of parameter changes can be undone.


ArcSyn Synthesizer Init Button

Sets all parameters to plain vanilla settings.


ArcSyn Synthesizer Random Button

Creates a random variation on the current program together with a random name. Certain controls, such as MASTER (Volume) aren't affected. Because the random function only varies the existing program, it works best with more complicated programs. Each time it is clicked, it starts from the original program.

Holding the SHIFT key while clicking RANDOM will produce a near-total randomisation of all parameters.

Note: It's probably a good idea to turn ArcSyn's MASTER volume down when experimenting with RANDOM if you like your speakers!


Selects one of two downsampling filter types, BRIGHT or SOFT. SOFT is the original (v1.0.0) type, but BRIGHT is the default choice as it sounds cleaner and brighter and uses slightly less CPU power. This setting is saved globally.



ArcSyn Synthesizer Master


Adjusts the glide time. The button next to the knob switches between EQUAL TIME and EQUAL RATE modes. The default time is 1ms which is short eough to be inaudible, the default mode is EQUAL TIME.


Adjusts the glide slope. When set to less than 0% the glide will start fast then slow down (like most analogue synthesizers), when set to more than 0% it will start slow then speed up. The default setting is 0%, or a constant (in octaves) rate.


Selects the way in which ArcSyn's 32 voices are assigned to incoming MIDI notes.

The remaining ARP voice modes use only the 1st voice and play held notes in order at the rate set by the ARP RATE menu. Envelopes are only triggered by the ist note played.

ARP RATE New in v2.0.0

Selects the rate at which note pitches are selected in any of the ARP voice modes. This menu is only visible if an ARP voice mode is currently selected.


Selects the range of MIDI pitch bend pitch-bend modulation. These settings have no effect on the pitch-bend modulation source in the mod matrix, which always ranges from -100% to +100%. The default value is +/-2 semitones.


Selects the current MIDI channel. This value is saved separately for each instance of ArcSyn. The default value is OMNI, or all MIDI channels.


'Illuminates' (in white) when MIDI data is received.


Selects MIDI learn mode. Send a MIDI control message to ArcSyn, move a control and it will be paired. The default setting is OFF. MIDI learn pairings are saved globally so all instances of ArcSyn will share them.


Clears all MIDI learn pairings.


Adjusts the master tuning. This fine-tunes the whole sound engine of ArcSyn up or down by a maximum of half a semitone so it can be adjusted relative to other plug-ins or other instances of ArcSyn. The default setting is 0%.


Adjusts the master (post effect) volume. The default value is -12dB. Note: the output of ArcSyn (since v1.3) is limited to 0dB by a soft-clipping stage.


ArcSyn Synthesizer Oscillator


List of waveforms with detailed notes.

There are 71 waveforms. The default waveform for oscillator 1 is SAW, for oscillators 2 and 3 it's OFF.


Adjusts the "shape" of oscillator waveforms. Some waveforms have fixed shapes, for example the SAW so the SHAPE control won't have any affect on these and the display will show -. In other cases, such as PULSE, the SHAPE can be continuously adjusted. In other case the SHAPE selects between a fixed number of options, for example HARMONICS.

SHAPE L/R Buttons

Increases or decreases the SHAPE setting in discrete steps. The step size varies according to the particular oscillator waveform selected, for example there are 32 CHORD steps and 64 WAVETABLE steps. The default number of steps is 16.

Note: The shape L/R buttons are useful even for continuously-variable waveforms like PULSE, as it allows multiple oscillator waveform shapes to be set to exactly the same amount.


When turned on, RESET will cause an oscillator's phase to reset to zero with each new note. Useful if you want a consistent attack for each note. ArcSyn's RESET affects every waveform, including noise, which means the noise will be exactly the same on each new note. The default value for RESET is OFF.


Each oscillator has OCTAVE and SEMITONE tuning controls. If you click on the readout, you get a menu from which to select a new value, if you click the L/R arrow buttonsArcSyn Synthesizer Inc-Dec Buttonto either side of each readout, the OCTAVE or SEMITONE value is increased or decreased by 1. The range is -4 to +4 OCTAVES and -11 to +11 SEMITONES. If you try clicking the SEMITONE number past "11", (or "-11") it resets to zero and the OCTAVE value goes up (or down) by 1, until you reach the maximum possible transposition value.


Each oscillator has EXP and LIN detuning controls. The EXP control gives standard detuning which speeds up as you increase the oscillator pitch, the LIN control gives a different detuning which has a constant beat rate as the oscillator pitch goes up and down. You can use both options at once. LIN detuning is useful to give more 'analogue' warmth to a sound by causing octaves to go slightly out of tune.

Note: There is a small, random amount of detuning applied to each note played by ArcSyn to give it a more natural sound. this is especially useful if you're using the ROTATE voice mode.


Adjusts the oscillator level. The default setting is 100% for oscillator-1 and 0% for oscillator-2 and 3.

1 - 2

Adjusts the balance of the oscillator output sent to filter-1 and 2. The default setting is 50%.


ArcSyn Synthesizer Filter


List of filter types with detailed notes.

There are 37 types which are selected with a menu. Most types have adjustable RES (Or Resonance, or Emphasis or Q, or...) which usually adjusts the resonance but in some filter types does something else. The CUTOFF control adjusts the filter frequency and all filters have the same range *EXCEPT* the FORMANT filter, in which the CUTOFF control adjusts the current vowel sound.


Adjusts the cutoff frequency of each filter, except the VOWEL filter where it adjusts the vowel sound. All other filters have the same frequency range, which is 16.3 Hz to 25,110 Hz, or exactly one octave higher than the oscillator range.


Adjusts the amount of RES (or resonance or Q or feedback or emphasis...) for each filter. A few filter types don't respond to this control, notably the ALIAS filters.


There are 8 types, which are selected with a menu. You can use the DRIVE feature even if you've selected the OFF filter. The drive is positioned after the filter as it sounds a lot more interesting that way - distortion does little to a raw SAW wave and nothing at all to a PULSE wave other than messing up our finely-tuned antialiasing!


Adjusts the amount of cutoff modulation from ENV-1. If it is set to 100% it can modulate the cutoff over its entire range. The default setting is 0%. Note: if you want to modulate filter-2's cutoff with a different envelope, try routing ENV-2 to FILTER-2 using the Modulation Matrix.


Adjusts the amount of cutoff modulation from the MIDI note input. If set to 100%, the cutoff tracks the note input exactly. The default setting is 0%.



Adjusts the filter output level. The default setting is 50%.


Adjusts the balance between Filter-1 and Filter-2 outputs. The default setting is 50%.

1 - 2

Adjusts the level of signal from Filter-1's output to Filter-2's input. This signal is taken before Filter-1's LEVEL control so it will work even if Filter-1's LEVEL is set to 0%. This allows the filters to be arranged in series (or in a hybrid series-parallel arrangement). The slider increases the signal from Filter-1 as it is moved down, which matches the visual layout of the filters.

Note: To arrange the filters completely in series, slide 1 - 2 down to 100%, then slide BALANCE down to -100%. You can also move the individual OSCILLATOR 1 - 2 sliders up to 1 if you want to send all the oscillator signals to Filter-1.


ArcSyn Synthesizer LFO

This is the complicated bit! There are 8 LFOs selected with the 1-8 number buttons on the left. Each LFO is capable of playing not just single waveforms but also sequences of up to 16 waveforms. Each sequence step also has a STEP LEVEL control which generates a stepped output, sometimes called a 'stepper'. The current (active) sequence step is shown by the LFO waveform display as yellow on black [*], inactive steps are grey [*].

Note: Click the waveform display to select LFO waveforms. Adjust the SHAPE control to alter the waveform shape or select between different waveforms in a set like RANDOM-VAR-1 (which has 16 different random waveforms).


Adjusts LFO frequency. There is a button to the right of this control which selects between beat-sync and normal modes. In beat-sync mode, the control is a menu, in normal mode it is a knob.


Adjusts how much offset is added to the LFO output. If you're doing something like vibrato, you probably want the LFO output to be balanced equally about zero (the central, default position), if you're doing note sequencing you probably want it to be entirely positive.


Adjusts how long the LFO takes to fade up from zero when a note is played. This applies even in MONO mode.


Selects what happens when a note is played:



Selects MONO or POLY LFO modes. In MONO mode, all the voices share one LFO, in POLY mode, each voice has it's own LFO.


Shows the LFO waveform. Clicking this display opens a menu from which the LFO waveform can be selected. The LFO sequence step currently active is highlighted in black and white.


The horizontal slider underneath each WAVEFORM DISPLAY. Adjusts the LFO waveform shape or selects between discrete shapes - watch the parameter display to see what's going on :-) As with the oscillator SHAPE control, if the current waveform is a fixed shape which can't be adjusted, the parameter display will showArcSyn Synthesizer Off Display.


Selects the number of active sequence steps (1 to 16). The default setting is 1.

LEVEL (The numbers under the waveform display)

Adjusts the level of the LFO output in semitones (0 to 127). The default setting is 127 for LFO step 1 and 0 for the remaining steps.

STEP LEVEL (The bottom row of numbers)

Adjusts the level of the LFO step output in semitones (0 to 24). The default setting is 0.


The R arrow buttons ArcSyn Synthesizer Blob Button next to LFO step numbers 1-15. (There's no button next to step 16 because it has nowhere to paste to!) Clicking this button copies all the LFO waveforms up to and including the current step to the remaining active steps. For example, if you've set the SEQUENCE LENGTH to 8 steps, clicking the COPY/PASTE button on step 1 will copy step 1's waveform to steps 2-8. If you click the COPY/PASTE button on step 5 it will copy steps 1-3 to steps 6-8—it won't copy steps 4-5 because they would have to go after the end of the current sequence (step 8).

To delete waveforms, try setting the SEQUENCE LENGTH to 1 then clicking step 1's COPY/PASTE button—it will clear steps 2-16 because the sequence is now only 1 step long.


The R arrow [*] buttons ArcSyn Synthesizer Blob Button next to the LFO WAVEFORM LEVEL numbers ArcSyn Synthesizer Numbers (Grey, top row.) These buttons work in the same way as the WAVEFORM copy/paste buttons but work with the WAVEFORM LEVELS. See COPY/PASTE WAVEFORM above for detailed explanation.


The R arrow buttons ArcSyn Synthesizer Blob Button next to the LFO STEP LEVEL numbers (Grey, bottom row.) These buttons work in the same way as the WAVEFORM copy/paste buttons but work with the STEP LEVELS. See COPY/PASTE WAVEFORM above for detailed explanation.


Copies all settings from the current LFO.


Pastes all LFO settings held in the COPY buffer to the current LFO. The Parameter Display shows which LFO's settings have been copied, or the OFF ArcSyn Synthesizer OFF Symbol symbol if no LFO has been copied yet.

Quick LFO Sequence Tutorial

You can select different LFO waveforms for each step as well - the LFO level numbers (second to bottom row of grey numbers) will adjust their pitch modulation depth in semitones. Or you could start with one of the factory programs which uses LFO sequences. There's a very simple 4-step note sequence in the INIT bank.


ArcSyn Synthesizer Envelope

There are 4 AHDSR envelopes. ("H" stands for "Hold") ENV-4 is pre-patched to the main output level and ENV-1 is pre-patched to FILTER-1 & 2 cutoff modulation. The SLOPE horizontal sliders above the A-D-R controls adjust the curve of the envelope slopes - the central position gives linear slopes. All times range from 2ms to 20s.

A (Attack)

Adjusts the ADHSR ATTACK time, which is the time it takes to reach the peak level after a MIDI note begins.

H (Hold)

Adjusts the ADHSR HOLD time, which is the time it stays at the peak level. If the note is released during the HOLD time, the Envelope will switch to RELEASE.

D (Decay)

Adjusts the ADHSR DECAY time, which is the time it takes to decay to the SUSTAIN level after the HOLD has finished.

S (Sustain)

Adjusts the ADHSR SUSTAIN level which is the level which it stays after the DECAY has finished.

R (Release)

Adjusts the ADHSR RELEASE time, which is the time it takes to decay to zero when a MIDI note ends.


ArcSyn Synthesizer Effect


List of effect types with detailed notes.

There are 32 types which are selected with a menu. All types share controls wherever possible—for instance, choruses, flangers and phasers all share the same LFO controls. Most of the controls are (hopefully!) fairly self-explanatory. As usual, watch the parameter display—every control has its own readout.

Note: To temporarily turn an effect off, click its labelArcSyn Synthesizer Effect Nameif you save a program with an effect turned off in this way, those effect settings will not be saved.


ArcSyn Synthesizer Routing Button

There are 2 effect routing modes, SERIES and PARALLEL. In SERIES mode, effect-1 is fed from the effect L and R busses in stereo—effect-1 then feeds effect-2 then effect-3. In PARALLEL mode, the L filter bus goes to effect-1, the R filter bus goes to effect-3 and effect-2 is fed from the combined outputs of effect-1 and effect-3. The default setting is SERIES.


ArcSyn Synthesizer Effect Swap

Swaps the position of effects-1 and 2, or effects-2 and 3 when clicked. Useful when experimenting with effect ordering, which can change the sound of a program significantly. This will also swap any effect parameter modulation destinations which have been routed in the modulation matrix.


There is a stereo audio input bus to the effects section. ArcSyn's effects section is live all the time so it isn't necessary to trigger notes to use this feature. Its useability depends on your DAW/sequencer supporting audio inputs to VSTi and AudioUnit plug-ins.


ArcSyn Synthesizer Modulation Matrix

The modulation matrix allows modulation sources (like LFOs) to be routed to modulation destinations (like FILTER FREQUENCY). Each slot (row) allows up to 2 sources (A and B) to be selected and combined together using MODIFIERS. There are a large number of modifiers, ranging from simple addition to musical quantisation. The default modifier setting is OFF which will just add sources A and B together.

There are 16 modulation slots but only 8 are shown at any one time. To access slots 9-16, click the vertical numbers to either side of the modulation matrix. Click again to switch back to slots 1-8.

IMPORTANT! If you want the LFO output to be in tune, you have to turn the modulation AMOUNT to maximum (100 %) in the modulation matrix when modulating oscillator pitch.


List of modulation sources with detailed notes.


List of modulation modifiers with detailed notes.


List of modulation destinations with detailed notes.


Displays ArcSyn's version number for a few seconds when first opened, then the value of any control as the mouse pointer is hovered over it. Also displays ArcSyn's version number when the mouse pointer is hovered over the parameter display itself.


Displays the licensed user’s name or DEMO MODE - SOOTHING NOISE.


Steps through the available GUI skins. There are currently 3 skins, the factory skin, one by Layzer and one by Satyatunes. Skin selection is saved globally so will affect all instances of ArcSyn.

• GUI control descriptions marked with [*] refer to the appearance of those controls in the factory GUI.


The UNISON section is under the program name display. The menu allows selection of 1 (OFF) to 16 unison copies of all 3 oscillators. The detune slider allows the amount by which the copies are detuned to be adjusted. Detune sets the maximum difference between the lowest and highest unison copy, irrespective of how many unisons there are.

System Requirements

Win: a PC running Windows 7, 8 or 10 with an SSE2-capable CPU and a VST 2.4 or VST3 compatible DAW / sequencer host application.

Mac: an Intel Mac running 64 bit macOS 10.7 (Lion) or later and an AudioUnit, VST 2.4 or VST3 compatible DAW / sequencer host application.


If you've upgraded from ArcSyn v3.0.0 or earlier, you can delete the old ArcSyn folder, which is no longer used, from: Mac: ~/Library/Application Support/ (To find your Library, open the Go menu then press ALT - "Library" will appear in the menu) Windows: C:\Users\YOU\AppData\Roaming\

Version History

Version history.

Known Issues

ArcSyn won't run in macOS Big Sur. We are working on a fix for this issue which should be available before the end of 2020.

ArcSyn runs in GarageBand 10 but won't load any factory programs due to 'sandboxing'. A workaround for this is to move (or symlink) the ArcSyn folder from ~/Documents/ArcSyn to ~/Library/Containers/com.apple.garageband10/Data/Documents/ArcSyn. This will make presets load and save correctly.


ArcSyn design, DSP and yellow/grey GUI copyright © 2024 Steven Cook, SPC Plugins. All rights reserved.

Default factory GUI by Satyatunes. Alternative GUI by Layzer.

Thank you to MetaDronos, Marc-Olivier Johnson, Miro Pajic, Simon Field, Tom Wies, Allen Terhune, Andre LaFosse, Ed Ten Eyck, and Richard DeHove for beta testing and design suggestions. Jürgen Haible (RIP) for inspiration. Special thanks to Ace Layton. Thanks to Martin Finke for GarageBand program workaround. VST plug-in technology by Steinberg. Some icon designs from Picol. All trademarks are the property of their respective owners.

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