First, welcome to the forum !!.....and, as far it goes for the OS.....well, when Ketron released the 4.0a version, you had 2 options, one was to keep the original sounds and just ge the new functions.
The other one was a larger one, it will put new sounds ( I installed and I like it a lot), besides the new functions, of course, you need about 12 or 13 floppys...and follow step by step.....and you will not have problems. After that, followed the versions 4.0b and now the 4.0c.......go to the Ketron web site ( Italy) and download the OS of your choice and the instructions.
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mdorantes
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mdorantes