A very good point about the levels, and that goes for both the out-signal from the keyboard as well as the in-signal to the tapedeck.
Be careful with the out volume on the KN, keep it low rather than too high. Adjust and watch the tapedecks peak in a testrun, then record.
If there are a "automatic peak level limiter" on the tape deck, don't use it, rather do it manually, because in my ears it destroy the music.

Why edit out boinks and doinks Bud? I think it is a kind of charming when it's not too "streamlined" as most of the factorymusic that we can hear nowadays seems to be.
But of course, if you're planning to enter the Top Twenty lists ........
GJ