Sloppy or not, Dylan is astonishingly prolific; he has written more than five hundred songs. Most of them are lovely (or angry or joyous or wickedly sly or all of those things together). Many of them are unforgettable. (A new album, Dylan’s forty-fourth, called “Modern Times,” is being released this month. The songs are simple riffs, with laid-back arrangements, and all feature prominently Dylan’s gorgeous late-period croak. It sounds a little the way “Buena Vista Social Club” might have sounded if Cuba had been the birthplace of the blues.) The only comparable pop songbook from the era is Lennon-McCartney—and there were two of them. Dylan is also, despite the silly things people said about his voice when he started out, one of pop music’s greatest vocalists. His chief weakness is a tendency to shout, particularly in performance (and he is, let us say, an inconsistent performer); but, when he is in control of the instrument, no one’s voice, with that kind of music, is more textured or more beautiful.