I don’t know if this is helpful, but I tend to write about things I’m trying to better understand or develop and, in writing, furthering that development or understanding. It’s often said to write what you know, and while I think it’s helpful to approach writing with some base of understanding (usually through reading the work of others or whatever other means of exposure–obviously through artistic and musical practice in this case), it’s perhaps most compelling for the reader and the writer to experience a sort of organic unfolding of ideas in the course of a text. I think that by the end of a piece of writing, there should be something like a broadened field of inquiry open (again, for the reader as well as the writer), which is often paradoxically accomplished in gathering together disparate bits of information and collecting one’s own thoughts on the matter; this can be likened to how so many areas science, culture, industry, etc. coalesce in the engineering, assembly, and launch of a rocket, often all for the common purpose of exploration.
I think I apply this generally across my writing (and had never put it such-ways until just now, incidentally), but in the case of my writing about music (which is never purely academic, because it directly influences my musical practice), I’ve applied it in exploring the significance of the electronic form of music and had to learn quite a lot of the history and much regarding the technical aspects of electronic sound in all its forms and was also given to abandon many assumptions about the duality of art and craft, for instance (though admittedly, the seeds of this learning and shedding of assumptions had preceded the work). However you go about it, writing is an excellent way of organizing thoughts and to catalyze the process of thinking about whatever it is that commands your attention, and though the musical form can be sharply distinct and even at odds with the written word as a creative practice, you’re likely to find much that is expressible bound up within that form, or certainly behind it.