Definitely a controversial topic in terms of making the simple things quite complicated problems.
So, what is so "evil" about music then?
Music is a patternized sound that can bring about pleasure in hearing it (or from the consequences of hearing it).
Hmm. When you hear something which eventually annoys you, even if it is something as primitive as a continously loud noise, then you want to avoid it. This can be associated to something "evil", though I wouldn't jump to such a scary word such as that.
One music might be liked by person A and might be disliked by person B (and not just because of personal taste - it might be because it reminds them of something personal, like a traumatic incident), so in this way, Person B can attribute the music to be "evil".
So what is the "issue" of music in Islam?