In the 14 years I've been writing about and reporting on African music, I've learned to pay attention when musicians with a mainstream audience show any glimmer of interest in the subject. After all, it takes a lot of articles, reviews and radio programs to match the impact of, say, Paul Simon's Graceland in terms of opening American ears to Africa. So I was intrigued when in 1998 I learned that Bonnie Raitt, one of the most admired figures in American blues pop, had recorded a song inspired by Oliver Mutukudzi of Zimbabwe...