Overview

This document introduces cesSynth2, a VST2 plugin which models a drawbar organ. The synth offers the following features:

• Polyphonic - up to 64 notes can be played, with a polyphony limiting control
• Nine harmonics, with individually selectable levels. There is an additional a detuned oscillator for each harmonic, with a user selectable detune level.
• Full ADSR control of the amplitude.
• Stereo output, with pan controls for each oscillator, and an autopanning control
• Control of the detuned oscillators
• Click simulation
• Percussion simulation
• Resonant LP filter
• A custom GUI

A free version of the plugin can be downloaded from here for Macintosh and here for PC. The plugin comes with a default sond bank. The free version is released under the feedbackware licence agreement. In addition, a version can be purchased for $20 from here which adds sample accurate sync.

If you have any comments of this documentation, or the plugin, please contact me.

Optimising the synth performance

It is possible to configure cesSynth2 to produce some very complicated sounds. Some aspects of the sound are computationaly expensive, and similar results can be achieved with significant performance savings.

The synth operates in the following modes:

Mode	PIII/500	G3/400	Description
No detune or pan		52	With the Pan Rate and Pan Depth set to 0, and the Tune Rng and Tune Lvl set to 0, the no detune or pan mode is selected, which offers the most polyphony.
No detune with pan		28	Tune Rng and Tune Lvl set to 0.
Detune		32	No pan, but individual drawbar detunes used.
Detune with pan		20	All synth features used.

From the above table is should be noted that there are significant performance gains to be had from not using detune, and not using pan. If a very simple pan is required (the same pan position for all drawbars), an external plugin can be used to provide this facility. This will offer better performance than the internal pan effect, since this calculates the pan for each drawbar separately.

It should be noted that the use of percussion, click or the ADSR filter do not affect the synth mode, or the synth performance.

Synth Controls

• The synth provides 9 harmonics. In the GUI, there is a slider for the output level of each harmonic. Under the slider is a knob providing a detune control for the harmonic, and under that a pan control. The overall width of the pan is controlled by the Pan Depth control.
• The envelope section provides a standard ADSR for the overall note amplitude.
• The pan section allows a pan depth (from mono to full stereo width) and an autopan rate. The pan rate moves the position of the harmonics within the stereo image at the indicated rate.
• The tune section allows the range of the detuned oscillators to be selected (maximum setting is 1 semitone), and the level of the detuned oscillators. It is therefore possible to produce 'beat' type effects by setting the level at maximum and detuning the oscillators by only a few hz. With large range settings, richer harmonic sounds can be produced.
• The Click controls give control over the total time of the click (in ms) and the click intensity. The click is applied to the signal before the envelope, so if you have a slow envelope attack, you won't get to hear the click.
• The percussion controls provide a time control, and a level. The level control runs from -100 to 100. Negative values add the 2 2/3' pipe, whilst positive values add the 4' pipe to the output. The percussion is not affected by the envelope, or the level selected for the given harmonic.
• The filter section provides a cutoff frequency and a feedback control.
• The poly control limits the maximum number of voices.
• The volume control controls the overall volume control of the synth.