Jazz is far too broad of a term to be used to describe any particular kind of music. Under that one word fall swing, bebop, cool jazz, acid jazz, free jazz, big band, fusion, blues, dixie land....just to name a few.

I was a music performance major for a few years and have been listening to and playing "jazz" all my life. About 70 percent (just a guesstimation) of all jazz you'll ever hear has no lyrics. For the other 30 percent that does it is easy to discern whether you can glorify God through listening to the music. For the majority, though, that has no lyrics we are presented with a dilemma. The listener, in my opinion, has a limited "musical license" to allow him to associate certain connotations with music. Obviously this isn't possible if the music has lyrics, or if the music is publicly known to have been written for a certain purpose or to promote a certain feeling. This too presents a problem, for we don't know the intentions of all composers.

For instance, I do not listen to or promote Richard Wagner because of his strong ties with Nazism. Another example, I really enjoy listening to John Coltrane who was converted later in life and composed/played music in regards to that. Most of the composers will not be that clear though, and that is where I think our musical license comes in.

So to answer your question, "is Jazz evil?" I would answer, "No, not in itself." But that is not an absolute answer. It's situational.