Speed of groove.

Precisely! That's all we are saying

Well, I understood this all along, but the original poster was talking about correlating the cartridge's output voltage with the linear velocity of the record.
This is the correlation I said I didn't understand and I don't believe exists.
Everything else is clear to me. Maybe I misunderstood the post itself, wouldn't be the first time... ;-)
There's variation in sound quality between outer tracks and inner ones, due to the in formation being more densely packed together on the inner grooves, but not "output level" differences. Nobody has to turn the volume up as the inner tracks are played.

Mihaitaa, I understood the OP as asking what the effects of the differences in tangential ("linear") velocity at different points on the record would be on the output of the cartridge, given that the cartridge output is spec'd based on velocity. The answer, as you realize, is that there is no effect, because what is relevant is stylus deflection velocity, not tangential groove velocity, and for a given signal stylus deflection velocity does not change as a function of position on the record.

12-30-11: Marakanetz
Would you consider a decreased performance on the inner groves normal in some of records especially fully "packed"?

Inner groove distortion is certainly recognized as a potential issue, but my analog experience is not extensive enough to make a general comment on how pervasive a problem it might be. You might want to start a separate thread on that subject, that will probably catch the eye of some of the analog experts we have here.

Regards,
-- Al

The answer, as you realize, is that there is no effect, because what is relevant is stylus deflection velocity, not tangential groove velocity

Splendid, that was exactly my point as well.
Happy New Year, everybody.