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

• An 8 stage crossfading oscillator
• Harmonic pitch controls for each stage
• Pan per stage
• Multistage, multimode filter
• 11 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 and additional 4Gb of sounds.

Please note that Quetzalcoatl is under active development, it is not a finished product. There will be bugs :). To avoid disappointment, consider downloading the free version first to make sure you get on with it.