This is going to start as a basic lesson in sound physics. I won’t get too dense right away because we just need to know how the saxophone (or any instrument) makes a noise and why it sounds like it does. From that point, we can start talking about how to manipulate the instrument to extend the instrument’s range and alter it’s sound by using extended techniques.
There are keys that down the body of the saxophone. These keys are precise plugs for the corresponding hole in the tube. The lowest a saxophone can sound is when every single hole on the horn is plugged and the highest when all keys are open (I’ll modify this later)