I think that background music can enhance certain kinds of blogs like
art or short stories. But, this subject has been covered before in
"How To Do It" so you should use the keywords "adding music to blog"
for discussions. However, I will tell you how I added music to my
blog. First, obtain a MIDI file for your music. Then, add the MIDI
file to a Toolbox folder on your personal website that your ISP
provides. Then, go into Blogger editor and add an HTML page element
to the top of your blog. Add the URL of the MIDI file to this element
and save. Then, your music will play as soon as the page loads. Hope
that helps. Come to my blog if you want to see that it can be done.