I wrote a CLI version of a sequencer (multitrack sequencing with plugins and automation where a simple xml format controls the sequencer events) a couple of years ago. I had a quite clear vision of what I wanted to achieve, and then picked C++ and JUCE and just started figuring things out.
I generally learn best by having a real thing to build; and then finding the resources I need when I get stuck.
I buy books aspirationally (I have bought the Audio Programming Book as well come to think of it) - so I often end up with many books on subjects that interests me, without learning much from them.