What is the blues? The blues is pain set to music. Take "I'd Rather Go Blind," the 1967 classic written by blues queen Etta James. Beaten by her drunken foster father, James spent time in Cook County Jail for forging checks to support her longtime heroin habit. You can hear it in her voice. Posing definite artistic challenges for singers who are not Etta James, such as a high school student from the Northwest suburbs. "Something toooooold me, it was oh-oh-ver," sings Nyrobi, 17, slowly, in a thi