Re: KN550
I will try to answer your question. Many moons ago I had a KN650 and I know that it wouldn't connect to my PC as it wasn't built for it. In those days we used MIDI to connect to other instruments, audio etc., and believe me it was considered very 'up market' to own a keyboard with a MIDI connection.
I believe there are cables out now that will enable Parallel and USB machines/instruments to be connected (e.g. an old printer with a modern PC) but as I said, I cannot recall the KN650 having the necessary socket on it to enable you to do this, whereas of course, the KN7 has a USB socket built into it.
In view of this, I wouldn't think it can be done with your KN550. I could be wrong and I daresay you will get some more replies to your posting from people who do know the correct answer to your question.
Good luck!
Audrey