Bob Dylan has never had to rely on the purity of his croon to get his vocal point across. But as the years have gone by, the grit in the great man’s voice has gone from fine to extra-coarse, to put things in sandpaper terms. (David Bowie terms, too: He famously compared Dylan’s voice to “sand and glue.”) Dylan has put his careworn vocal cords to a curious test on his newest album, Shadows in the Night, out February 3, which features songs made famous by Frank Sinatra and other golden-voiced singers. It sure seems like a bold choice, especially given his vocal limitations. For some medical background, Vulture reached out to otolaryngologist Dr. Milan Amin, director of the Nyu Voice Center, to get a medical explanation for why Dylan's voice sounds so rough, and if there’s anything that could be done to get things back to their...