This is a fairly standard essay setup. Your task is to come up with a thesis and support it in three ways. This would create the standard five paragraph student essay. The first paragraph is your introduction with thesis statement. The next three paragraphs contain your three supporting arguments, and the final paragraph is your conclusion. Based on the essay prompt provided in this eNotes question, the essay thesis is wide open. On one hand, this is nice because it gives you a lot of different directions that you could possibly take for your thesis and essay. On the other hand, it's frustrating because the prompt offers very little guidance.
My first piece of advice is to figure out what argument you want to make about music. You have to argue something in a thesis. It can't be a statement of fact, because then there is nothing to prove and support. You could argue that music is beneficial. You could argue that it is distracting. You could argue that modern day artists are simply taking old forms and putting a modern spin on them. It really is up to you.
Once you have a general idea of what your argument is going to be, you need to put it in a concise thesis statement. You do not want a thesis statement to be a rambling, long sentence. It needs to be somewhat direct, and it needs to set up your reader for the coming argumentative support. I like the two-sided thesis format that starts with the word "although." I like it because it sets up an argument and a counter-argument for the writer to discuss. For example: "Although much of modern electronic dance music is still very much considered underground music, it has begun to influence mainstream music in country, pop, and even rap genres."
This thesis is probably best supported in four body paragraphs. The first paragraph would explain what electronic dance music (EDM) is and why it is an "underground" form of music. The next three paragraphs would show how EDM is influencing those three particular music genres.