Grounding the keyboard should improve matters. The plug you show does have a ground connection but this comes from a pin sticking out of the mains socket, rather than the plug, or via ground strips on either side of the socket.
See:
https://en.wikipedia.org/wiki/AC_power_ ... nd_sockets
Look for CEE 7/3 socket (German) and CEE 7/5 socket (French). The plug is the CEE 7/7 plug.
In the background of the image you posted, there appears to be a UK style 3-pin plug. Either fit one of these plugs onto the cable, or get a ready made cable having that 3-pin plug on one end and an IEC connector for the Kronos end.
If you still experience the electical static feeling after doing this, check the earthing, and also check the condition of wiring around the property. If the property has been badly wired, you may be exposed to strong mains fields, where touching an earthed object will result in an electrical sensation.
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