Servo Controlled Arm

Dan_ed...The main points are as follows...
1...The arm pivots, just like a conventional arm. This prevents any side forces due to the servo.
2...The pivot point is moved as the record plays.
3...The rate of movement is biased to match nominal groove spacing.
4...Actual groove spacing different from nominal will cause a slight arm angle to develop. This is measured by a Hall effect sensor in the arm, and the rate of pivot point movement is adjusted accordingly.

I do understand those points, but it is still constantly hunting for the correct groove position based on reaction to what has already occurred. I just don't understand the "why do it at all". Perhaps there are others, but the only reason I can think of is that the designers have made the assumption that no conventional arm can track as well as this feedback control servo mechanism.

Whats worse an arm that can adjust its positioning if needed or an arm that is off and doesnt possess the ability or awareness to correct itself

What arm would that be? I don't know of any arm that doesn't self correct based on stylus position in the groove. Granted, some may do it better than others.

If I want to go down stream in a kayak, do I handle the paddle myself? Or do I through a line to two friends, one on either side of the river, and have them steer my kayak for me?

Dan_ed...If groove spacing changes abruptly there will be a momentary change in tracking angle WITHIN THE SPEC RANGE OF 0.5 DEGREES. (Remember, the arm pivots). A properly designed servo does not overshoot or hunt. Digital servos make it particularly easy to implement the necessary algorithms, which may be difficult or impossible to do with analog components.