My DX7 is still one of my favorite synths, sonically speaking. I had no idea how intuitive yet novel the circuitry was until I began reading this article.

In particular, I found it suprising that the sine waves were generated by indexing a wave table - you'd think a sine wave would be easy enough to generate without a table, but the way it implements phase distortion ('FM') on those sine waves by simply offsetting the index into that table is quite interesting. Sorta like having different mathematical functions for 'i' in a for loop.