Some books are hard work reading. While there is annoyingly often lot of fluff and filler in academic writing, density is not necessarily an indication of fast thinking, but is more often the result of slow and careful construction. For me, the fewer words, the better, and writing that way takes a lot of work. It does not seem to me the text you excerpted from is much about music at all. "Vocalization" appears to belong to a theory of inter-subjectivity.

I'm not sure if Derida is usually saying anything or not. In general, I don't find it worth the trouble to find out. But he has written some good pieces, including one about visiting his mother who was suffering from Alzheimer's and didn't recognize him any more. It's very beautiful. I have the feeling he was a poet masquerading as a philosopher, and that was a disservice to his art. In person, his personal presentation was very simple and un-presupposing, and lecturing, he struck me very much as a Kantian moralist, if slightly mischevious.

If you regularly find a few sentences as illuminating as you say here, then it's just a question of whether you want to put the work into studying in the field to understand more of it. You're right: it's hard work. And no one but you can say wether it's worth it.