Quetzalcoatl is a Harmonic Vector synthesiser plugin (VST/AudioUnit) for Mac OS & Windows. It features:

• An 8 stage crossfading oscillator
• Harmonic pitch controls for each stage
• Pan per stage
• Multistage, multimode filter
• 4 Multifunction modulation sources
• A large and diverse sound library

Quetzalcoatl is open source and the plugin and source code can be downloaded freely from my GitHub page, this listing is for an expanded version with additional sounds and presets.

Please note that Quetzalcoatl is under active development, it is not a finished product and there will be bugs :).