Ep9. What does it take to understand what is jazz?
What does it take to understand something? 
If you ask Amazon’s Echo, “Alexa, what is understanding?” she replies that “understanding is a psychological process related to an abstract or physical object, such as a person, situation, or message whereby one is able to think about it and use concepts to deal adequately with that object.” (bolded passages not stressed by Alexa)
So, to understand something is to recognize (a psychological process) and comprehend in an effective manner the subject, or process, or task to be accomplished. Any effective manner is always going to be relative to one’s goals.
Understanding something does NOT require understanding everything there is to know about the topic at hand. Instead, it is to have sufficient grasp on the topic to correctly answer questions about that subject matter (knowing that) or to manipulate the environment to satisfy particular goals (knowing how/techne).
At no time did the mechanic understand all there is to know about cars since ultimately this requires knowledge of subatomic particles and quantum mechanics (funny that!) and the answers, knowledge, and understanding of these topics are unresolved and not fully known.
Philosophers often make a distinction between knowing HOW (a skill) versus knowing THAT (so-called propositional knowledge). This distinction applies as well to understanding.
The jazz musician understands WHAT jazz is, even if she claims NOT to be able to define it. She knows when she is playing jazz that she is, and when she is not, that she is not. (If we leave aside “borderline” cases.) So the jazz musician understands HOW to play jazz, but also understands THAT she is playing jazz, when she is, which is techne versus a kind of self-knowledge.
What does it take to understand jazz? 
Applying these lessons to goals in the philosophy of jazz, what model can be anticipated for successfully understanding jazz and what makes some music qualify as jazz?
The investigation of the mechanic’s understanding of how to fix the car only required his recognition of some key features that enabled him to achieve particular and relevant goals, as in getting the motor running and you off to work. It did not require him to have knowledge of how to forge steel even though there was steel forging involved in the project.
PoJ.fm proposes to supply a partial understanding (there is rarely a full understanding of anything) of central topics and issues arising when characterizing jazz. If some good answers can be found and justified to questions about jazz, and especially how to define it, then this constitutes an understanding of what is jazz.
For a fuller discussion see Ontdef3. What is the definition of jazz?