Xvimbi,The keys are weighted with lead to achieve a specified touch weight across the keyboard,tapering in weight from bass to treble.Why?Because the :)hammers also taper in weight fromm bass to treble.If you were to look at the keys from the side,you would see that the keysticks in the bass have more lead,and this lessens as you get up into the treble.We must also consider another part of the equation,upweight.We not only balance for a specific downweight,but also for a target upweight,usually 20 or more grams,also tapering from bass(less) to treble(more).A well balanced keyboard gives the pianist the necessary control over dynamics and repetition.