Hi Gunnar,
unfortunately no. The Technics KN3000 hard drive system was a normal IDE drive but on a Technics board with a special interface and connector. This fitted into a plastic moulding on the back on the keyboard - a simple slot in.

The keysoft system was on a larger board, and you had to open up the keyboard and the plastic moulding was disassembled and discarded to create enough space for the larger board and new back panel parallel computer socket. The new board had to have around 5 or 6 wires soldered to the main microprocessor for interface in a specific cable layout. The drive was reformatted internally and the KN3000 then had pretty much the identical functions and new main load/save screen as the Keysoft KN5000 hard drive system you had.

Yes, thank you, the weather here is very fine. I was away last week and am going again next week , so "making hay" while this sun shines