I'm guessing you mean "nonfiction book," not "nonfiction novel," because this sounds like a compilation/encyclopedia kind of book, not a story with a beginning, middle, and end, although I guess a book like this could be written that way.
I have to admit I don't fully understand your theme, but I would suggest you start with a list, just off the top of your head, about the artists you think would be applicable to this book. Don't worry about building a comprehensive list yet. More names will come through your research.
Consider how many total you would like to feature and how long each entry should be. 1000 words? 1,500 words?
Since your subject will span decades, probably to the beginning of recorded music, start googling the names and see what's already been written about them. Obviously don't rely on opinion blogs for information, but these can serve as jumping-off points.
You'll also see entries highlighed in google books, which will give a good snapshot of books available online. However, these are not comprehensive and will likely be missing key pages that you may need for further info. Also, Billboard magazines are in google books, so you'll see articles and entries in those too.
Google-books doesn't include all books ever written. What you see online will serve as a partial resource. You should note their titles and authors and then go to the library and see if you can find both those books and other similar ones not featured online. And in those books you should find information about the artists in your lists that will not be available online.
If you're feeling especially brave, you can try contacting living artists by email or phone to see if they'll talk to you for insight. And if they do, they'll surely give you more names you can add to your list.
I'm thinking that a hundred would be a good list to shoot for.
Anyway, that's how I would approach it. Hope that helps.