When they cut a test record, do they cut it absolutely flat, or do they cut it so that it will measure flat when played with a magnetic cartridge and RIAA pre-emphasis/de-emphasis? Because if it's the latter, the only way you will be able to measure true cartridge response is for the playback system to absolutely mirror the curve of the cutting system, and if it doesn't, cartridge results are going to be skewed. That curve is theoretical, sometimes they get pretty close, sometimes they don't. All depends on your R/C tolerance. Of course cutting it flat would result in some pretty crazy grooves. And you thought the 1812 Overture was a wild ride? Just curious.