During all the rumblings about console automation (Allison, Olive, etc.) in the early seventies, I had the inspiration for Compumix (based on years of working with telemetry systems) while I was chief engineer at Quad-Eight. But the hardest part was finding a good VCA. I had developed a novel PWM/PAM unit - it converted input audio into 1 MHz PWM (using a single transistor and a TTL Schmitt trigger IC) and then used a pair of complementary MOSFET switches to modulate the PWM's amplitude in response to the DC control voltage. Then a simple low-pass filter recovered the audio. It worked really well, including a low noise floor, but it was hard to get the zero-control-voltage output to under about -80 dB because N and P-channel MOSFETs of the day were awful compared to what's available today. We made about a hundred of them (I still have one as a souvenir) that were used as sub-group faders on a few large custom boards back in the day. But the trimming required ruled them out for the Compumix system, so I was told to reverse-engineer a dBx 202 and we made our own version of the module until dBx became aware and Quad-Eight got the customary "cease and desist" letter from dBx's attorney. They were gracious enough to give us a favorable quantity price and we used the 202 in production Compumix systems. Compumix, an "add-on" mixdown automation system sold well - to A&M, Warner Brothers, Armin Steiner, Neil Young (who cut his "Time Fades Away" album directly from multi-track via Compumix), and many others. Compumix's "update" function apparently established a standard for using -15 dB as a reference point for updating a track's gain trajectory. Bud Bennett, owner of Quad-Eight back then, was notoriously stingy but, to my astonishment, gave me a bonus of half my yearly salary that year for developing such a successful product! It certainly wasn't trivial back in the day before floppy discs and single-chip processors!