A monophonic, virtual analogue synth voice


Interzone is a complete synth voice that has been designed to emulate a basic yet versatile monophonic, analogue synthesizer. It combines several 'bread-n'butter' modules into a single package that can operate by itself, or be part of a bigger system thanks to its external modulation jacks. Interzone has been designed with effiency in mind, employing inexpensive DSP techniques to ensure that there is little CPU usage where possible.

It has been a labour of love, and I personally hope that you get as much out of it as I did developing it.



Interzone is made up of smaller sub-modules that are connected together to form the complete synth voice. Below is a flowchart that shows how these are connected together.


User Guide

The major controls of Interzone have CV inputs available allowing for full automation of those parameters.



Interzone features one voltage controlled oscillator (VCO) that outputs 3 waveforms simultaneously: Saw, Pulse and a Sub wave. These waves are mixed using the mixer section discussed here. The VCO section in Interzone is where you control the tuning, pulse width, and modulation applied to the VCO's pitch and pulse width.



This section is where the VCO's waves, the noise and external input are all blended together. Each sound source has it's own dedicated fader that controls the source's level. The mixer is also where the Sub wave's octave and waveform is chosen, as well as the noise generator's type: white or pink.



The filter is key part of Interzone. It is a switchable 12/24 dB per octave, or 2/4 pole, OTA design, and saturates nicely if overdriven. The output of the mixer is passed into the filter, which is then cascaded into a highpass filter which can be used to tame some of the low end of the sound.



Whilst a VCO, a mixer and a filter can create a good sound, it can quickly become boring for the listener if the notes or sounds produced all seem the same. To add variety and movement to the sound, Interzone provides an LFO and an envelope generator. On the VCO and Filter sections, you will have seen sliders that allow for modulation from either the LFO or envelope generator. The VCO has options for pitch and pulse width modulation (PWM), whilst the filter features cutoff modulation.


The LFO features 7 waveforms, from sine through to noise.

Envelope Generator

The envelope generator is the usual, 4-stage ADSR type. This is hardwired to the VCA (though this can be switched on the VCA itself) to provide the overall shape of the level of a note.


Context Menu

This menu is accessed by right-clicking on any blank area of Interzone. The only available entry is the option to switch the panel from 'Dark' or 'Light', as is possible with all other Valley modules.