Vortex Sound Research

Good deal for learning the basics of synthesis by ear and by, ehm, (virtual) gear. I found the tutorials in the demo very helpful, to understand synthesis and start to train my ears as to how waveforms sound differently, and what all the basic modules do.

Highly recommended. And no, I have no dog in this fight, I just think that it's a great tool for learning the theory and practice of synthesis.

https://www.syntorial.com/

Note: If it's not cool to post such things here, I'll remove it.