Kurzweil K2500 - creating a complex pad using chaotic FUNctions 

Mathematics. *Seriously.* It's not wizardry though: The LFO (usually) is a simple sine wave, so for fun, just apply that to cutoff on a simple sawtooth. Simple enough right? You get a "wah-wah" on your wave that's set to whatever the sine wave interval is. That's easy enough. Now you know what a "cutoff function" sounds like, and you should have an idea of the squiggly s-shape of the LFO. The sine wave cycles up and down (for pretend here) between 1 and -1. Now, take the screen at 1:27. He's using LFO1 as an input a, he then assigns GkeyNum as input b. So the value of sine-wave modulation of the LFO at this point would be added (See the (a + b) setting on the far right?) to the integer corresponding to the key you play on the keyboard... -64 to +63 IIRC. So if you hit midi D0 and your LFO starts at the keypress at 1, then it starts out as (1 + 2) and the LFO will modulate whatever you assign it to (cutoff is audibly the easiest) and you can play with it there. It helps to visualize or even have access to a graphing calculator or wolframalpha.com. www.varsitytutors.com/hotmath/hotmath_help/topics/graphing-sine-function Now from there... you can assign FUN1 as an input to FUN2 which as you can see starts cascading in my ability to explain in words... But in this screen, assigning Input a of FUN2 as FUN1 injects the entire equation (SIN + a) into input A of FUN2. TLDR: Start learning how sine waves work as LFOs and experiment with different math relations and how they affect LFO's operation on cutoff... and go take Trig + College Algebra if you want to be able to predict wave forms on a calculator and then hear how they sound.

@@NunyaB1s Clear as mud

check out the full user manual and it gives you clear explanation of what each one does.

@@NunyaB1s or, look just look at a video of a sine wave and that changes the value of a variable up or down depending on how high it is. 1 sentence

@@wendigo2442 I think you'd prefer that advanced calculus class with that method 🤣