Informed by Jazz
The other day my wife came home and told me two of her coworkers had a debate about the genre of jazz. Wanting some pieces of wisdom to defend the honor of jazz, she asked my opinion, which got me thinking... Years ago, I wrote a piece called "File Under Jazz" and explained how jazz is today less a genre and more a process. As my career has progressed, and as I've played a wider variety of music in a professional setting, I've experienced this process more profoundly. While jazz gigs make up a smaller percentage of my performances, everything I play is informed by jazz.
To be informed by jazz is to approach a piece of music with a greater understanding of the underlying harmonic and rhythmic structure, and how it relates to the melody. Jazz musicians are trained to learn a song inside and out. They know how any note might sound over any chord.
This is a generalization, but when I play a gig with musicians with no background in jazz, many times they just learn their part. Their ear helps them find notes that work, but without really knowing where it fits in the grand scheme of the song. There is nothing wrong with this--if music sounds good, it sounds good!
When a jazz musician hears a song, she hears not just the notes being played, but all the notes that could possibly be played. You see, jazz originated from musicians playing a tune over and over again, adding more embellishment to the original melody with each pass. Improvising melodies in this way is, essentially, the heart of jazz music. The only way to begin competent improvising is to understand a song inside and out.
Of course, there are plenty of musicians that have never had any formal training in jazz, but I'd argue that if they approach a song as I've just mentioned, than it's fair to say they have been influenced by this process of jazz. A great deal of modern music over the last 50 years has been heavily informed by jazz--by the artists, studio musicians, composers, and producers who all had backgrounds in jazz. To study that music is to study results of the process I'm describing.
In summary, jazz is a sophisticated universal wordless language spoken between musicians. Since the late 20th Century, the language has been absorbed into other genres through musicians influencing each other. In return, the genre of jazz has been so heavily influenced by every other kind of music that when people have to use a multitude of subgenres and eras to clarify exactly what kind of jazz they enjoy.
If you don't like jazz music but would like to broaden your tastes, here's what I recommend: Instead of buying a some '50s era Miles Davis album and trying to force yourself to like it, start with some music that you already like, then find out what that artist listens to, and what everybody who plays with that artist listens to. Dig back through the web of influences far enough, you'll find some jazz you actually like and by that point, truly appreciate.
Photo credit: The great Kenny Burrell on guitar by Tom Marcello - see more great jazz photography on Tom's photostream.