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Update: 2020-06-15

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TrapezoidSynth

TrapezoidSynth is a monophonic synthesizer equipped with 2 trapezoid oscillator. Trapezoid oscillator is based on PTR (Polynomial Transition Regions) and it has a drawback that increasing noise at high frequency. Therefore 8 times oversampled. 2 pitch shifters are added to make some chord.

The package includes following builds:

macOS build isn’t tested because I don’t have Mac. If you found a bug, please file a issue to GitHub repository or send email to ryukau@gmail.com.

Linux build is built on Ubuntu 18.0.4 and tested on Bitwig 3.1.2 and Reaper 6.03. Bitwig 3.1.2 seems to have a bug that occasionally blackouts GUI.

Installation

Plugin

Place *.vst3 directory to:

DAW may provides additional VST3 directory. For more information, please refer to the manual of the DAW.

Presets

Extract preset zip, then place preset directory to the OS specific path:

Preset directory name must be the same as the plugin. Make Uhhyou directory if it does not exist.

Windows Specific

If DAW doesn’t recognize the plugin, try installing C++ redistributable (vc_redist.x64.exe). Installer can be found in the link below.

Linux Specific

On Ubuntu 18.0.4, those packages are required.

sudo apt install libxcb-cursor0  libxkbcommon-x11-0

If DAW doesn’t recognize the plugin, take a look at Package Requirements section of the link below and make sure all the VST3 related package is installed.

REAPER on Linux may not recognize the plugin. A workaround is to delete a file ~/.config/REAPER/reaper-vstplugins64.ini and restart REAPER.

Color Configuration

At first time, create color config file to:

Below is a example of style.json.

{
  "fontPath": "",
  "foreground": "#ffffff",
  "foregroundButtonOn": "#000000",
  "foregroundInactive": "#8a8a8a",
  "background": "#353d3e",
  "boxBackground": "#000000",
  "border": "#808080",
  "borderCheckbox": "#808080",
  "unfocused": "#b8a65c",
  "highlightMain": "#368a94",
  "highlightAccent": "#2c8a58",
  "highlightButton": "#a77842",
  "highlightWarning": "#8742a7",
  "overlay": "#ffffff88",
  "overlayHighlight": "#00ff0033"
}

Hex color codes are used.

First letter # is conventional. Plugins ignore the first letter of color code, thus ?102938, \n11335577 are valid.

Do not use characters outside of 0-9a-f for color value.

Controls

Knob and slider can do:

Right clicking on controllable object popups a context menu provided by DAW.

Caution

It is recommended to insert high-pass when setting SlideType to Reset to 0.

Block Diagram

If the image is small, use Ctrl + Mouse Wheel or “View Image” on right click menu to scale.

Diagram only shows overview. It’s not exact implementation.

Parameters

Oscillator Common

Semi

Change oscillator pitch in semitone.

Cent

Change oscillator pitch in cent. 100 cent = 1 semitone.

Slope

Change left and right side of slope of trapezoid.

PW

Pulse width. Change length of upper side of trapezoid.

Oscillator 1

Drift

Modulate pitch with white noise.

Feedback

Modulate phase of Oscillator 1 with feedback signal.

osc1Phase += Feedback * (osc1 + OscMix * (osc2 - osc1))

Oscillator 2

Overtone

Multiply the frequency of oscillator by number of Overtone.

PM

Modulate Osillator 1 phase with Oscillator 2 output.

Envelope Common

Retrigger

When checked, reset envelope for each note on. When not checked, reset envelope only if the number of pressed key is changed from 0 to 1 or more.

A

Attack time in seconds.

D

Decay time in seconds.

S

Sustain level.

R

Release time in seconds.

Curve

Change envelope curve.

Gain Envelope

Gain

Master output gain.

Filter

Order

TrapezoidSynth is using 8 of serially connected first order filter. Order changes where to get the signal from the filter.

Cut

Cutoff frequency in Hz.

Res

Resonance.

Sat

Filter saturation.

filterInput = tanh(Sat * (input + Res * filterOutput))
Env>Cut

Modulation amount from Filter Envelope to Cut.

Key>Cut

Modulation amount from note pitch to Cut.

+OscMix

Modulation amount from mixed signal of Oscillator 1 and Oscillator 2 to Cut.

Filter Envelope

>Octave

Modulation amount from Filter Envelope to pitch in octave.

Misc

OscMix

Ratio of Oscillator 1 and Oscillator 2. When turned to left-most, output becomes only the signal from Oscillator 1.

Octave

Change pitch in octave.

Smooth

Interpolation time in seconds from previous value to current value. Following parameters are affected by Smooth.

Mod Common

Retrigger

When checked, reset envelope for each note on. When not checked, reset envelope only if the number of pressed key is changed from 0 to 1 or more.

Attack

Modulation envelope attack time in seconds.

Curve

Modulation envelope curve.

Mod 1

>PM

Modulation amount from modulation envelope 1 to Oscillator2.PM.

Mod 2

>Feedback

Modulation amount from modulation envelope 2 to Oscillator1.Feedback.

>LFO

Modulation amount from modulation envelope 2 to LFO.Freq.

>Slope2

Modulation amount from modulation envelope 2 to Oscillator2.Slope.

>Shifter1

Modulation amount from modulation envelope 2 to Shifter 1 pitch.

Shifter Common

Semi

Change amount of pitch shift in semitone.

Cent

Change amount of pitch shift pitch in cent. 100 cent = 1 semitone.

Gain

Output gain of pitch shifter.

LFO

LFOType

4 waveforms are available for LFO.

Tempo

Synchronize LFO frequency to tempo.

Freq

LFO frequency.

Shape

Change LFO wave shape.

>Pitch

Modulation amount from LFO to Oscillator 1 pitch.

>Slope1

Modulation amount from LFO to Oscillator1.Slope.

>PW1

Modulation amount from LFO to Oscillator1.PW.

>PW1

Modulation amount from LFO to Filter.Cut.

Slide

SlideType

3 type of pitch slide is available.

Time

Time of pitch sliding.

Offset

Oscillator 2 slide time with respect to Oscillator 1 slide time.

Change Log

Old Versions

License

TrapezoidSynth is licensed under GPLv3. Complete licenses are linked below.

If the link above doesn’t work, please send email to ryukau@gmail.com.

About VST

VST is a trademark of Steinberg Media Technologies GmbH, registered in Europe and other countries.