Purchase and install SynthEdit, a modular drag-and-drop VST creation software, or download the free demo. The free demo allows you to design and save VSTi format virtual synthesizers. The full retail version of SynthEdit offers customization and expanded design options.
Open SynthEdit and create a new synthesizer project. Create a container in the blank field by right-clicking and selecting "Container" from the "Insert" menu.
Edit the contents of the container by right clicking "Container" and selecting "Structure." The new dialog box that appears represents the inside of the container. Create a MIDI CV, or MIDI Control Voltage, by right-clicking the blank field and selecting "Insert > MIDI > MIDI CV." Physical synthesizers work by directing voltage through circuits, and SynthEdit creates virtual synthesizers by visually representing virtual circuits and voltage.
Connect the MIDI-to-CV module to the existing IO Mod in your container by clicking and dragging a virtual path from the MIDI In port on your MIDI-to-CV module to the IO Mod and releasing the mouse. The software automatically creates a MIDI Out port on the IO Mod. This allows your synthesizer to receive MIDI data to control playback.
Create an oscillator by right-clicking the blank field in your container and selecting "Insert > Waveform > Oscillator." An oscillator creates the synthesizer sounds by producing a variety of waveforms internally. All analog synthesizers function by control and filtering of basic oscillators.
Connect the MIDI-to-CV module to your oscillator by clicking and dragging a virtual pathway from the Pitch port on the MIDI-to-CV module to the Pitch port on the oscillator.
Add an ADSR2 component by right-clicking the container field and selecting "Insert > Waveform > ADSR2." Connect the MIDI-to-CV module to the ADSR2 component by clicking and dragging a virtual pathway from the Gate port on the MIDI-to-CV module to the Gate port on the ADSR2 component. The ADSR2 unit allows you to control the Attack, Secay, Sustain and Release (ADSR) of the oscillator.
Insert a VCA module by right-clicking on the container field and selecting "Insert > Modules > VCA." Connect the audio out of your oscillator to the VCA module and the signal out of your ADSR2 component to the volume of your VCA Module.
Create another IO Mod by right-clicking the container field and selecting "Insert > IO Mod." Connect the output of the VCA to the IO Mod you just created.
Create four sliders by right-clicking the container field and selecting "Insert > Controls > Slider." Connect one slider to the Attack of the ADSR2 component, another to Decay, another to Sustain and the final slider to Release. Right-click the container field and select "Panel Edit" to arrange the sliders visually.
Return to the container by exiting the Panel Edit menu and insert a List Entry dialog by selecting "Insert > Controls > List Entry." Connect the List Entry dialog to the waveform port of your oscillator. The List Entry field selects the type of waveform produced by your oscillator from a list of seven possible waveforms.
Close your container and return to the original field. Add a sound out element by right-clicking the field and selecting "Insert > Input-Output > Sound Out." Connect the output of your container to ports one and two of the sound out. Connecting to both ports one and two creates a stereo playback.
Test your synthesizer by selecting "Insert > Controls > Keyboard" and connecting the MIDI Out of the keyboard to the container. Click the keys of the keyboard with your mouse and listen for playback. If playback is satisfactory, select "File > Save as VST" to create a virtual synthesizer.