" How complected is the tone generator and is it possible to make one that you can tweek the frequency?"

You can do that and a whole lot more...sound effects for instance....But it takes time, study and a workbench.

Once you start....you get addicted. One circuit leads to another.

 

Would this work for generating the tone?

https://www.amazon.com/dp/B016LPE4P...t=&hvlocphy=9030244&hvtargid=pla-348703474539