Entry level signal generation

What would you suggest would be a good way to start exploring signal generation? There are so many different ways to make an oscillator, I just don’t know where to start, or what would prove to be worth while.

I have played with 555’s and 40106’s to make a digital square output, and I followed that pretty well, but am ready for something a little more in depth. Looking at proper VCO schematics scare me, but I would like to get there someday.

Thoughts?

Look at triangle core oscillators (the type used for LFO with square/triangle out) - a tri-core VCO is a bit less difficult to “get right” than a saw-core, and the path between a static-frequency oscillator and a current/voltage controlled one is smoother…

Does the LM137 make a tri-core VCO? You had said before to start with OTA’s and work up to more complex things.