Tracking error
The angle by which the tracking of the record diverges from the tangent line is called tracking error. The tracking error leads to non-linear distortions because the signal from the horizontal groove is slightly distorted by the tonearm not being tangential to it. The extent of the distortions depends not only on the tracking error, but also on the specific radius of the record and the music signal itself.
If the pivoted tonearm is well adjusted, the tracking error can be less than ± 2°. With a tangential tonearm the tracking error depends only on the precision of the manufacturing and on the correct adjustment and mounting of the pick up.