Motorised Sliders
In the old days when you adjusted the volume (Physical) sliders to balance your sounds, they could not be stored in presets, and therefore you had to rebalance the sound with the sliders every time you changed a preset. (In those days the quality of the sounds were not great and so an optimised sound balance was not so critical)
Things improved over the years, and the later instruments allowed the position of the volume sliders to be stored in a preset, the down side was that when you changed presets, although the volumes changed, there was no indication of where the sliders were positioned when the preset was stored.
The way some manufactures got round this, was to actually fit motors to the sliders so that when you selected the preset, the motor moved the slider to the correct position.
The first time I saw this, was about 1981/2 when Yamaha bought out the FS series Organs/Electones, (All based on the DX7 Synth) unfortunately when the HS series was introduced in about 1985, they reverted to touch pads with LED indication. (Much cheaper to produce)
I hope the above helps to allow people to understand, what is meant by motorised sliders.

Bill