Sytrus is a powerful and versatile synthesizer featuring six customizable oscillators (operators). It can perform FM (Frequency Modulation), RM (Ring Modulation/Amplitude Modulation), Subtractive and Additive synthesis. It includes 3 filter modules, an effects module with chorus, three delay lines and unique, per-voice programmable Unison envelopes.

Along with this flexibility comes complexity. However, if you stick with Sytrus and study this help file (there's a easy step-by-step tutorial here), we are sure you will find Sytrus to be one of the most rewarding plugins in the Image-Line library.

Want more sounds? - There are a large number of user created Sytrus patches available on-line in the dedicated Sytrus Presets & Tips Forum.

See Sytrus video tutorials on Image-Line's YouTube channel.


Sytrus Main Module

The main module contains some global settings for the current patch. It provides less experienced users with easy to use global filter and volume envelope levels, allowing them to adjust the existing patches to their preferences, even if they lack experience in the programming of FM synthesizers.

Main Module Options

Sytrus - The Operator (Oscillator) Module

In FM Synthesis Oscillators are called 'Operators', this is because they can be used to modulate other operator (oscillator)s. The operator (oscillator) modules are central to the Sytrus synthesis engine as this section is used to define the operator shape and pitch. The module supports full articulation section (envelopes and mappings of volume/pitch/phase, etc.)

Oscillator Settings

Sytrus - Working with the Harmonics Editor

The operators in Sytrus contain a fully-featured harmonics editor in which you can define an oscillator shape with up to 128 harmonics, either by drawing the harmonics manually or by analyzing external samples. Working this way to produce waveforms for the Oscillator is an example of Additive Synthesis. A harmonic is a sine-wave that is an exact (integer) multiple of the starting frequency (in this case 1,2,3,...128). Harmonic Editors allow you to perform 'additive synthesis', in which you mix together harmonics (upper facing bars) and adjust their phase (downward facing bars). Using this technique you can create any type of waveform.

Sytrus - Working with the Envelope Editor

The Envelope Editor may be used to adjust the articulation settings of a module including all envelopes, LFO and mapping charts. Sytrus envelopes are very customizable - each envelope segment can consist of unlimited nodes and segments, each with customizable tension (acceleration). The articulator combines the best of multi-point envelopes and more simple ADSR envelopes with special section markers that allow for ADSR automation. Section markers can also be used to create arpeggios which can also be defined within envelopes.

Common Functions & Editing

Although there are several different types of envelopes and maps in Sytrus, they all share common functionality, as described below.

How to Add a Marker:

Right-click the control point where you want to set the section marker. From the menu select the marker you want to add. If the item you want to add is disabled make sure the marker is in the correct place (e.g. a sustain loop start cannot be placed after a sustain loop end).

To make a DL marker, simply check both the Decay and Sustain Loop Start entries in the Right-click menu.

How to Remove a Marker:

Right-click the control point where the marker is placed and uncheck the item representing the marker name. Keep in mind that removing some markers might make another marker/s redundant or cause them to be removed automatically (e.g. if you remove the sustain loop end marker, a sustain loop start marker will become redundant).

Envelope/Mapping Types

There are few types of envelopes/mappings which define the articulation of a specific property: ENV, LFO, KEY M, VEL M, etc. The only exception is WS (WaveShaper) in the filter module (as described below).

ADSR Envelope (ENV)

This is a "classic" ADSR envelope which combines the ability to define a sustain loop section with the power to create unlimited spline segments and refine various envelope sections as needed. Besides the editable envelope curve, the envelope also provides the regular envelope level controls, allowing you to lock the curves and still adjust some basic aspects of your envelope. All values are applied relative to the curve defined in the editor.

NOTE: When adjusting ADSR properties you can preview the effect of the knob value on the envelope shape. However, once the mouse key is released the envelope is restored to its previous view. The knob still has an effect, although it is not reflected in the curve to avoid distortion and make editing easier.

For more information on the available envelope sections (attack, decay, sustain, sustain loop, release) and how to define/remove a section marker, see Envelope Sections (ADSR) above.

Keyboard Mapping (KEY M)

With keyboard mapping you can define how the controlled property is offset depending on the keyboard key (note) pressed to generate a voice. At the bottom of the graph you can see the keyboard range (the highlighted range matches the range displayed by the integrated Sytrus keyboard).

Velocity Mapping (VEL M)

With this graph you can define how the voice velocity value relates to the controlled property.

Modulation X/Y (MOD X and MOD Y)

These two graphs allow you to map the values of the integrated X/Y controller (in the main moduke of Sytrus) to changes in the controlled property.

Random Mapping (RAND)

The random mapping lets you define the amount of randomization to the controlled property (one random value per voice is generated). This may be useful for simulating a live performance or the subtle inaccuracies of old analogue synths.

A random floating point number is selected for each voice, in the range of 0% to 100%. The curve lets you define how the random number relates to changes in the controlled property. The more curve "dots" there are for a particular vertical position, the more likely the value will be selected by the random generator, thus allowing you to fine tune the behavior or the random generator and effectively defining the "chances" of certain values being selected for each voice.

Unison Mapping (UNI)

This mapping is used by the unison feature of Sytrus (see the main moduke for more information) and it has effect only if the unison mode is enabled for the current patch.

The unison mode works by triggering a user-defined number of subvoices with altered properties for each actual voice in the sequence. Unison mapping lets you define how the controlled property varies across each of the sub-voices inside the unison.

By default the unison uses only its global variation levels (if enabled), as specified in the global settings. By defining a mapping curve in this unit you can have much greater control over the type and amount of variation of both the property and the module.

WaveShaper Mapping (WS)

This is the only articulated property defined by a single mapping and is available in each of the filter modules. The curve defines how the signal is distorted by the WaveShaper features in the filter modules, i.e. the original input levels and how they relate to the processed output levels.

Sytrus - Arpeggiator

Sytrus has a unique method of creating arpeggios (Arps). Arps are defined by Envelope (usually volume, modulation or filter) arpeggiator 'break-points' that can be applied to the Envelope nodes. See Working with Envelopes for more detail on the basics of Envelope manipulation and also where you can open the Envelope Sequencer Tool.

There are three types of Envelope Break Points used in making arpeggios (the middle three in the picture left), Previous, Same, Next. The first and last nodes relate to the loop start and end points (Loop Sustain start and Loop Sustain End respectively).

When a chord is played and the envelope is set to arpeggiate, each of the notes in the chord is played in turn within the envelope loop, as defined by the Arp break-point flags. Arp break-points are described in more detail below.


To add or change an Arp break-point, Right-click on the envelope node and select 'Arpeggiator break' from the popup menu, then select one of the following break-point types from the sub-menu.

Making an Arpeggio


Sytrus - The Filter Module

The Filter Module has 13 filter modes and many options that you can tweak to get the perfect sound for your project. It includes a complete articulation section that allows you full control over the filter parameters. The module also includes waveshaping distortion with customizable mapping.

NOTE: The Filter Mode switch is automatable and the SVF filter is capable of handling 3 filter modes simultaneously - low-pass, band-pass and high-pass.

Filter Controls

Modulation Envelopes (Articulators)

The articulation section allows you to apply an envelope, LFO, map keys, velocity or unison mode voices to a set of pre-defined properties. For a full list of envelopes/mapping in the Articulation section and their descriptions, see envelope editor page.

The filter mode supports the following articulation targets (controlled parameters):

Sytrus - The Effects Module

The effects module offers high-quality chorus effect, 3 delay lines which can process either in parallel or in serial (with the possibility to send the module output to a mixer send track for further processing) and a reverb section.

Effects Controls

Effects Articulation

The articulation section allows you to apply an envelope, LFO, map keys, velocity or unison mode voices to a set of predefined properties. To see the full list of envelopes/mapping in the articulation section and their meaning, please check the envelope editor page.

The filter mode supports the following articulation targets (controlled parameters):

Sytrus - Basics of FM Synthesis and the Modulation Matrix

Most of today's software synthesizers use a process known as 'subtractive synthesis' - a spectrum-rich oscillator (saw, square, triangle, etc.) is processed with a low-pass, band-pass, or high-pass resonant filter to produce the final sound. FM (Frequency Modulation) uses a different approach - pure tones (sine waves) processed in such a way that additional harmonics are created (one sine wave modulates the frequency of another) and added to the signal to produce the final sound. Unlike with Subtractive synths, the basic sound generating module of an FM synth is called an 'operator', which includes a pure tone oscillator (sine wave) and an articulation section. It is called an operator because it can do more than just create sound, it is also a modulator and so 'operates' on other operators.

FM synthesizers contain two or more operators (Sytrus supports up to six operators). When an operator is connected to the input of another, a pitch (frequency) modulation occurs (see diagram, above). The modulating operator is known as the 'modulator', while the modulated operator is called a 'carrier' (in Sytrus a single operator can act both as a carrier and modulator).

Sytrus Implementation

Sytrus offers everything found in classic FM synthesizers and supports up to six operators and a modulation matrix, in which you can define the synthesis algorithm. Sytrus also includes a set of advanced features which allow you to create many unique sounds:

NOTE: If you want to create your own Sytrus patches or modify existing ones, it is recommended to check the Sytrus processing diagram. It describes in detail how the Sytrus modules are processed and mixed:

The same diagram is quickly accessible from a button on the Sytrus interface:

The Modulation Matrix

The modulation matrix in Sytrus allows you to set up the FM synthesis algorithm and to adjust the operator send levels for effects and filter modules, and panning and 'dry' output levels.

SUPER IMPORTANT POINT: You can't automate the knobs in the FM or RM matrix. However, for FM you can automate or modulate the Volume knob (VOL) on the Operator (Oscillator) Module. This has the exact same effect as modulating the matrix knobs since you are changing the amplitude, and so amount of the Frequency Modulation.

Each matrix knob controls a specific function or mapping (as explained below). The neutral position for each knob is the middle Use Alt + Left-click to reset a knob to its neutral position. You can also Right-click a knob to quickly mute/unmute, while preserving the knob value (this feature is useful when testing and tuning a patch)

The modulation matrix comprises several discrete parts. Below we will take a more detailed look at each section and its applications:

Modulation Setup

The FM/RM section programs the modulation algorithm in Sytrus. Each row represents an operator (oscillator) and determines which operators will modulate it and by how much. The knob settings determine the amount of modulation - if the value is negative (turn the knob left) the modulation phase will be inverted. At the neutral level (Alt + Left-click a knob), there will be no modulation. It is not necessary for an operator to be modulated in order for it to produce output. When the Modulation matrix is in the Inactive state, Sytrus is acting as a Subtractive synth (with Additive oscillator control, of course).

Some FM routings and their representation in the Sytrus matrix:

In these examples, Operator 1 is used as a carrier while the rest of the active operators are modulators. You can modulate an operator by itself (in Example 3 - row 2, column 2 - modulating Operator 2 by itself), thus creating a feedback effect. Note the carrier must be assigned an output, either directly (as in the examples), or via the filter modules. For more information on filters and output assignment, see the other two matrix sections covered below.

NOTE: If you're unsure of the purpose of any knob in the matrix, simply hover your mouse over it and check the FL Studio Hint Bar.

Ring Modulation

Sytrus also supports RM (ring modulation) interaction between operators, which is a form of Amplitude Modulation. To see and adjust the RM setup, click the FM/RM switch at the bottom of the matrix:

In RM mode the amplitude of the target Operator is modulated. You can confirm this by Ring Modulating an operator by another, set to a very low frequency. Similar to FM, when amplitude is modulated at high-frequencies (audio rates) new tones / harmonics are generated. In RM mode the knobs adjusts the amount of signal sent from each operator to the filter modules. Negative values will send an inverted signal to the filter modules.

NOTE: The RM switch only affects the modulation type and routing section of the matrix. The rest of the settings (pan, FX send, filter send, etc.) are shared among the FM/RM matrices.

Filter Send Levels

Sytrus includes three filter modules. Each row in the section represents one module. If you want to send 50% of the output from operators 3 and 4 to filter section 2, adjust the knobs as follows: in row F2 (filter section 2), adjust the knob in column 3 (operator 3) to 50%; in the same row adjust the knob in column 4 (operator 4) to 50%. To reset a knob to a neutral position, use Alt + Left-click.

NOTE: The output of the filter sections must be assigned an output. To learn more, see the Pan, FX Send and Output section below.

Pan, FX Send and Output

Set the panning, effects send and output amounts for each of the operators and the three filter sections. The first column sets the panning of its corresponding module (operator or filter). The default position is center. The second column defines the amount of signal sent to the effects module. If you set this knob to a negative value, an inverted signal will be sent to the effects module. In the default neutral position (middle), no signal is sent to the effects module. The third column defines the output amount for its corresponding module (operator or filter). A negative value will send an inverted signal to the output.

IMPORTANT: Neither the operators or filter modules in Sytrus produce audio automatically. You'll need to use the matrix to rout them to the output stages as follows:

  1. Assign an output level for the module from the matrix section.
  2. Assign an effects send level for the module (the effects module is automatically sent to the output).
  3. (operators only) Assign the operator a filter send level via the Filter Send Levels matrix section (see above). The filter module you send to needs to 'reach' an output by itself.
  4. (Filters only) Use the Send to Next knob (see the filter module page for more info).

Sytrus Tutorials

Download this PDF

We recommend downloading - Sytrus Synthesis Manual - 2nd Edition by Jens Malmgren.

Overview of FM Synthesis

FM Synthesis is typically regarded as black magic by many synthesizer programmers. The Yamaha DX-7, the first popular FM synthesizer, was reported to have 90% of maintenance returns complete with their presets intact. You have probably browsed through the presets in Sytrus, and wondered, 'how did they do that'?. The next step, then, is usually to search the Internet for FM synthesis tutorials, only to discover that most of them tell you how to program a Yamaha DX7, or a particular DX7-like FM synthesizer to achieve a handful of particular sounds. But there's no clear idea how those "FM fundamentals" apply to Sytrus'. This tutorial will help remove some of the mystery from FM synthesis in general, and help you on your way to understanding what all those mysterious controls and knobs in Sytrus do.

See Sytrus video tutorials on Image-Line's YouTube channel.

Operators, Modulation Matrix, or Filters.

This tutorial is all about the Sytrus FM synthesizer, and the purpose behind the most important controls on its variety of control panels. This tutorial will not discuss each knob and slider, and how each individual control affects the output signal. However, after proceeding through this tutorial, you will understand:

Step 0: Learn about subtractive synthesis basics

It's fairly easy to get a basic grip on FM synthesis. Starting with simple waveforms, filters and envelopes are applied to get different "effects" on the final sound. With most subtractive synthesizers, you can pick a knob at random, tweak it, and likely hear a difference in the sound that comes out as a result. The 3xOSC plugin is a great place to start. Once you're comfortable with terms like, "oscillator", "LFO", "cutoff", and "ADSR", you may proceed.

Step 1: Understand what you're looking at in Sytrus

  1. Add a Sytrus channel. Click the "plug" in the upper left of the window, and select the "Default" patch. This patch produces a pure sine wave output. Ignore the 9x9 matrix control on the right side of the window for now.
  2. Click the "MAIN" box in the upper left to see how the synthesizer's overall characteristics are defined. These parameters operate on the signal that comes out of the synth/filter/pan/fx module. You can apply an overall volume and filter envelope, tweak the basic EQ, add a unison effect, and determine which parameters are affected by the x/y modulation controls.
  3. Click on the "OP 1" box towards the top of the window. This panel defines "Operator #1". An operator is simply a waveform; some audio signal. You can see one cycle of it in the box in the upper left. The sliders and knobs to the right of the waveform display allow you to modify some characteristics of the waveform. The row of buttons, "PAN", "VOL", etc. allow you to modify the characteristics of the waveform. "OP 2" through "OP 6" allow you to define five more waveforms.
  4. Click on the "FILT 1" box towards the top of the window. This panel defines "Filter #1". The panel and rows of buttons allow you to specify the characteristics of a filter, which can be applied to the output of the operators. "FILT 2" and "FILT 3" allow you to define two more filters.
  5. Click on the "FX" button towards the top of the window. This panel defines a basic effects chain consisting of panning, chorus, three delay units, and reverb.

Step 2: Sytrus, the Subtractive Synth, part 1 - The Sawtooth Wave

As a first step in learning how to program the Sytrus synthesizer, we will examine its capabilities as a subtractive synthesizer. This will build on our knowledge from Step 0, above, as we start to learn how to find our way around Sytrus without getting too complicated.

  1. Go back to the "OP 1" panel, and slide the "SH" slider (just to the right of the waveform display). As you slide it up, the waveform will change from a sine wave through triangle, saw, and square patterns, ending up with a square pulse. Set the slider in the middle of its range (50%) to produce a sawtooth wave. Play some notes and listen to the buzzing of all the high frequency components in the sawtooth wave.
  2. Now we'll take a look at the modulation matrix. In the Default preset, only one knob is activated. On the far right of the OP1 row, the knob in the "OUT" column is turned all the way up, to 100%. This knob indicates that the output from OP1 should go straight to the output at full volume. Each of the top six knobs in the "OUT" column indicate how loud each of the operators should be in the output mix. The bottom three knobs indicate how loud the output from each filter should be in the output mix.

Step 3: Sytrus, the Subtractive Synth, part 2 - a basic filter envelope

  1. Now, we'll apply the default filter to the saw wave in operator 1. First, Right-click the OP1 output level knob to mute it. Play some notes. Note that there is now no output from Sytrus. At least one of the various output knobs must be turned on to generate any output. So, to activate the output of filter 1, turn the output knob on the F1 row up to 100%. Play some notes. Note that there is still no output from Sytrus. At this point, we're sending 100% of the output from the filter to the output. However, there's no input signal to the filter, so no sound will be generated.
  2. To send some of the OP1 signal to the first filter, turn on the knob in the first column of the F1 row, and set it to the full on position, 100%. This sends the output of OP1 to the first filter. The output knob in the F1 row sends the output of the first filter to the output module. Play some notes. The default filter, applied to the saw wave produces a cheap synth horn sound.
  3. Activate the cutoff envelope for the first filter. Click on the "FILT 1" button toward the top of the window. This displays the Filter 1 settings. Click the "CUT" button in the middle row of buttons. This displays the parameters for the filter cutoff envelope. Click the "ENV" button to display the default envelope. Just under the bottom of the graphical envelope display are four knobs to set the Attack, Decay, Sustain, and Release parameters of the envelope. To the left of these four buttons, is a small, hollow radio button. The default setting is "off", indicating no filter cutoff envelope should be applied. Click the radio button to activate the filter cutoff envelope. Play some notes. Note how the cutoff envelope alters the sound of the "horn". Experiment with the ATT, DEC, SUS, and REL knobs to see how they alter the sound of the wave.

Step 4: An Introduction to Modulation

Step 5: Sytrus, the FM synth, Simple Modulation

  1. First, deactivate the filter by Right-clicking on the OP1/F1 knob. Re-activate the OP1 output by Right-clicking on the OUT/OP1 knob. Play some notes. The sound should be that of the original, unfiltered, buzzy, sawtooth wave.
  2. Now, apply some modulation to the sawtooth wave. First, play some notes to get a feel for the unmodulated sawtooth wave. Now, click the knob in the OP2 column of the OP1 row, and turn it to a setting of 25%. Play some more notes. Hear how the buzzing quality has changed slightly. Turn the modulation knob from 25% to 50% and hear how the quality of the sound has changed again. Try settings of 75% and 100%.

    Congratulations! you've now created an FM synth patch.

Step 6: Filtering a modulated signal

  1. Now, we'll apply the filter we created above to the FM modulated signal. Deactivate the OP1 output by Right-clicking on the OUT/OP1 knob. Make sure the OUT/F1 knob is activated. If not, Right-click it to activate it. Activate the OP2/F1 knob by turning it to 100%. Play some notes. The sound will be that of a pure sine wave. What's going on here?

    Well, what we actually did is route OP2 (an unmodulated sine wave) into Filter 1. Operator 2 is still at its default setting of a sine wave, so the output generated is a filtered sine wave, or, in other words, a sine wave. What we wanted to do is send OP1 into Filter 1. (This may be the most confusing feature of the modulation matrix itself.) This is part of what I mean by OP1*OP2 not being the same as OP2*OP1. Since we configured OP2 to modulate OP1, in order to send the modulated OP1 output to a filter module, we must use the OP1 column of the desired filter row to route that signal accordingly.

  2. To route OP1 into Filter 1, deactivate the OP2/F1 knob by Right-clicking on it, and re-activate the OP1/F1 knob by Right-clicking on it. Now, we are routing the modulated OP1 signal into the filter. Play some notes. Now, the filter we created above is acting on the modulated signal.

Step 7: The single difference between FM and Subtractive synthesis

    Subtractive synthesis uses richer waveforms (triangle waves, square waves, etc.) as the base signal before applying filtering, resulting in higher order harmonic content in the synthesized signal. FM synthesis creates richer waveforms via modulation, resulting in "sidebands" of the carrier signal (i.e. the operator being modulated). That's it. Both use filters, envelopes and modulators on the sound. Once you understand what the knobs in the modulation matrix do, you're off and running. FM Synthesis can seem intimidating because it does not seem as intuitive as basic subtractive synthesis. The 'sidebands' resulting from the modulation operations are not as easily visualized as relatively simple square waves, or triangle waves. Also, FM synthesizers typically have much more complex envelopes and automation capabilities (see the 'Electrocution' preset for a complex automated filter example), adding to their complexity and intimidation factor.

Tutorial credits: Eric Mitchell.

Sytrus - Notes & Tips to Patch Creators

Please check the following recommendations to ensure that the patches you make are immediately usable, merge with the other presets, & don't waste CPU power, when it can be avoided at no quality loss:

Other Tips

Sytrus - Options and Helpers

Left-click on the symbols to open the following features:

  1. Options / Presets - Contains a menu with several items as described below:
  2. Show information - This shows the Sytrus version and information screen, to revert to the normal Sytrus user interface Left-click on the screen again.
  3. Show block diagram - This shows the Sytrus internal signal routing diagram. Click the user interface again to return to the normal Sytrus interface.
  4. Show keyboard - This shows/hides the preview keyboard.

Plugin Credits

Code: Didier Dambrin.

Vectorial UI: Miroslav Krajcovic

Vectorial Sytrus logo: Valentin Prados

VSTi port: Frederic Vanmol.

Many thanks to: Bram (oversampling), Jaha (for showing the wrong path :), Antti, Robert Bristow-Johnson (for making their filters public) , and all the ones who designed presets.

Reverb by: Ultrafunk.