This is a special music keyboard - the keys are large, mechanically resistant and have coloured light signalling.
The keyboard withstands rough handling (e.g. a blow with the fist).
The special ARCUS keyboard also has coloured light signalling.
A total of 512 colours can be chosen.
This light signalling may indicate:
whether the button is currently being pressed,
the meaning of the keys (dominant notes and subdominant notes of the scale are marked) - in order to easily find a way when playing freely,
light commands from the computer software, e.g. instructing the player to play the selected song (lighting up the note to be played).