Originally posted by: amnesiac 2.0
it positions the head up or down a very tiny bit to compensate for mis-positioning of the tape itself, AFAIK.
Originally posted by: dman6666
Before autotracking, the wheel would let you manually adjust the angle of the head to the tape. Now it's automagically done but they sometimes have an override (and sometimes Not--I hate that).
Diagrams and explanation here. Pretty interesting, never read it before!