Youll find that most tehnical terms in this sort of text can be directly adopted without translation. Certainly "Punch-in", "Event-editierung", "Flanger", "Expander", "Pan" and "Balance" dont need translation (indeed cant be translated really). Most musicians will understand "Step" as a recording mode, you could replace it with "Schritt" however. "Upper tones" I would translate word for word with "obere Töne". The manuals of an organ are "Register" in german, so the draw-bar section is the "Ziehregister", but (especially if you are talking to pop/rock musicians) "drawbar" would be understood. If you need any info on what these things actually *are*, drop me a line.