Stylus Drag

Atmasphere is correct.
You may not consciously 'hear' stylus drag as pitch change......but there are so many subtle clues embedded in the grooves which rely on perfectly stable speed control.
Remember that only half the analogue signal is contained in the record......Amplitude.
The 'Time Domain' to complete the sine wave is provided by the turntable rotation.
Any deviation in perfect speed results in a distorted sine wave just as if your amplifier was distorting?

And yes.....I have noticed via the Timeline....that heavily modulated passages cause more stylus drag than others.
I can see this effect on my Raven AC-2 quite clearly whereas on the Victor TT-101......the quartz-controlled DD motor compensates without any visual clues.

Newton's First Law of Motion:-

The velocity of a body remains constant unless the body is acted upon by an external force.

'Friction' is an 'external force'. Why do you think a motor is required to keep a platter spinning?

I personally can't imagine a platter that only weights even 5-10 pounds being slowed down enough by a short complex passage, to be bothersome.

Don't imagine it..........get a Timeline and SEE it!

Dear Nikola,
Actually the Raven is not that bad.
Using the Timeline......I found that two motors (opposed) actually kept a more constant speed than the three motors.
So that's how I now use it.
I think that stylus drag is a common factor for all belt-drive TTs....even those with string-drive and very heavy platters. Read how Dover, with his Final TT had to adjust the speed controller when the cartridge hit the vinyl?
I also had to do the same on the Raven.
In other words.....the speed of the TT is different with a cartridge tracking than without.
The TT-101 however......keeps the same speed regardless of whether there is a cartridge or not.....or even if there are multiple cartridges in contact with the record.

Incidentally......I also find that low compliance cartridges like most LOMCs.....have more stylus drag than high compliance MM s.
This may be why I hear less distortion with most MMs than I do with LOMCs?
Regards

Regarding the greater stylus drag with low compliance MC cartridges......I suspect it is also related to the higher tracking forces generally required with those over the MMs?

Good question my friend.
J Carr would certainly have an answer if he was lurking?

Where is the feedback mechanism in a Raven turntable?

I do agree with Dover......that the better your TT becomes at maintaining accurate and constant speed under heavily modulated passages.....the more you tend to hear the imperfections of the record pressings such as off-centre holes?
For every solution.....another problem is revealed :^(