Most modern day disc mastering lathes include a specialized computer. This computer varies the spacing between grooves and their depth of cut into the lacquer or copper in direct metal mastering. And the disc mastering engineer has some control over the parameters of the disc cutting computer. For instance, it is generally the norm to combine both channels to Mono below 250 Hz. This is done for a myriad of reasons. Plus high-frequency limiting is also generally employed because the RIAA requires heavy high-frequency preemphasis on the cut. With an inverse high-frequency deemphasis from a RIAA playback preamp. On old Scully lathes, the cutting engineer had to manually adjust the screw for the grooves spacing. Which generally meant, you would get less time per side than what a computer could deliver with a Neumann VMS 70 computer-controlled disc cutting lathe. Along with how much filtering the disc cutting engineer deemed necessary to create the most highly compatible disc for playback from the rest turntables with moving coil elliptical cartridges to $29 record players with ceramic cartridges and Sapphire needles instead of diamonds. Of course the volume is adjusted by the cutting engineer. And your cuts that have the most high frequencies in them should be at the beginning of the disc. Cuts with less high frequencies should be at the end of the disc. Higher frequency response is not as good the closer you get to the center. That's because the disc is actually moving faster at the outer ridge and slower at the inner ridge. And since high-frequency response suffers toward the center, the Cuts that are most abundant in high-frequency energy should be at the outer extremities. You can only cut so deep into lacquer. And the disc cutting engineer has to establish that limit first. This will also affect all of the other cuts level since they must use a unique form of normalization so that each cut is not too much louder nor softer from the previous to the next. It doesn't matter how you think it should be it matters what they must do. Just because you think something should be right one way doesn't mean it is to the disc cutting engineer.

In years before the CD was invented, disc cutting engineers would put together their filtering, limiting, level matching to cut the lacquer with. And then, they would make a second generation down safety backup of what they did, to another reel to reel recorder. So one that Stamper finally died or they needed to have their other subsidiary labels around the world also making stampers from a fresh lacquer cut, it would be the same as the producers had wanted it to be in the original release. And some folks would complain about that because the master is now another generation down that the lacquer is being cut from. So, more noise, more wow, more flutter more frequency response variations, NAB vs. CCIR, Etc.. So you might be making pre-Masters for some time but you ain't doing the cutting. So no record can have the same amount of time cut on both sides due to the different and varying program content. I'd be concerned if you are cutting the same thing on both sides and found a discrepancy in the density and amount of surface area utilized. But with different program content on both sides you'll always have a discrepancy in available length. There is no way to even that out. I mean you don't tell your own computer where you think the electrons should be going. It is already programmed to know where and how fast things should be moving about inside your computer. I mean why don't Mac & Windows machines turn off instantly, when you select shutdown? I mean what do they need to move around before shutting off the power when you've already created a blank screen? I want a computer to turn off when I tell it to not to sit around and think about doing it before it does it. What's there to think about? Turn off dammit! NOW! I'm waiti