I'm fairly sure there's a distinction, just not sure exactly where the line is. Again, there's no substitute for confirming the intent of the license with the musician, but I'm almost completely sure that simply fading in and out does not count as derivative. You could replace the music with some other piece of music and it wouldn't directly affect the meaning of your video. Compare editing the footage to match beats etc.

Not being able to use CC-licensed material would kind of defeat the whole purpose of CC, which is why I suspect your use is legit. In fact I think it's the whole point of CC!