[walto2]

> A second-order digital filter requires what, about 4 stores, recalls, and multiplies per sample?

This is true today using something like the Chamberlin form for a state variable filter. I don't think that level of optimization had been discovered yet in the DX7 timeframe.

Also, for adequate quality you want to oversample at least 2x, preferably at least 4x.

And 16 bits usually won't be enough headroom in a digital filter for good audio quality. Too much truncation.

[SeanLuke]

Well, remember the DX7 was 12 bit.

[walto2]

Right. My point was, digital filters won't sound good with those constraints, so people weren't using them yet.

Not to overshadow the main idea. The DX7 was a heck of a milestone.