Last night I stumbled upon this story
about how the LM13600/13700 operational transconductance amplifier was created. Interestingly, it is a pretty blatant rip-off of the 3080 series chip, and was mostly made as an exercise to learn IC design! I particularly liked this image, which is a hacked together solder prototype of the chip:
The LM13600/13700 has now outlasted the 3080, and is a totally vital chip for synths because of its voltage-controllability. It also has really nice clipping characteristics. It's somewhat common in analog synths, but I'm surprised it isn't completely ubiquitous. The page also has a lot of great links to application examples, including articles and the very helpful datasheet (scroll to the bottom).