Tonight's wikipedia spiral reading about how audio filters are actually implemented in electronics has not hit a brick wall, unlike many of the other times I've tried to teach myself basic EE concepts, mostly thanks to http://lushprojects.com/circuitjs/ . It's great to have a way to play around with the things I'm trying to understand which does not require me to go out and buy a bunch of physical things --- blech! --- definitely appeals to me as someone who has been permanently spoiled by the corunucopial copiability of software since long ago. So.... I think I kind of understand how to use op-amps, now, at least a little.