For me music in a demo reel can add so much. It can bring a good reel to life and make it great. It adds an extra dimension and gets your heart racing and excited about the prospect of creating something equally as stunning. For that I’ve always thought I’d add music to my reel when I make it.
However.. as has been pointed out, crap music can really ruin the whole thing. It’s not even about the quality of the music – It’s what the viewer thinks of it personally.
All in all my opinion has been changed. Right now I wouldn’t add music unless I was convinced it added to the reel. Even then I’d have you guys act as my test monkeys to see if I should use it or not. :)