The recording cutter head forms a tangent with all parts of the record groove by moving across the disc in a straight line, whereas the reproducing pickup traverses it in an arc. The axis of motion of the stylus is thus different to that of the cutter over a large portion of the disc surface. This is lateral tracking error, which produces second harmonic and intermodulation distortion.
"Thanks so much for converting my 42-year old Bar Mitzvah audio-tape to CDs. For such a solemn occasion, I couldn't stop laughing! Hearing my high-pitched, Texas-twanged Hebrew is such a treat; I would never have recognized that the boy on that tape is me. Surely my parents and sons will get a kick out of hearing this voice from my past."