What you are calling Horizontal Tracking Angle is probably what is usually referred to as Tracking Angle Error
Thanks - I did "invent" the term Horizontal Tracking Angle for myself to reflect the symmetry with Vertical Tracking Angle, but then I found out that ChatGPT knew what it was anyway. Can't tell what came first, so I've assumed HTA was widely used.
Given the symmetry, there are two errors that might be named Vertical Tracking Angle Error and Horizontal Tracking Angle Error. Because stereo grooves are almost always cut at 45-degrees, each of these errors should be equally important to both the left channel and to the right channel. Anyone disagree with this statement?
So why is so much discussion directed at VTA while HTA is ignored? If VTA is important, then surely HTA should be just as important.
I can't help but think that since almost all tonearms are pivoting, commercial interests are at play - after all, there's no point highlighting a weakness in your product design unless you can do something about it.
Friction-free tangential arm designs like the Holbo effectively eliminate sideways (skating) forces as well as HTA errors. And there is no headshell offset or bent tonearm either ![]()

