Tom Waits has had quite a career trajectory, starting out with fairly conventional folk songs in the early 1970s, before becoming a jazzy crooner grounded by one of the most gravelly voices in popular music, to eventually transitioning into what sounds like the spokesman to a carnival ushering in the apocalypse. Waits has always been interested in exploring themes of isolation and death, focusing on deadbeats, alcoholics, and lost souls, but it was really with the 1992 album Bone Machine that he truly became a troubadour of the End Times. The songs on Bone Machine are even more unhinged than his previous work, which had started to become more and more unconventional, the songs are carried by sparse instrumentation and clanging, awkward percussion. His 1999 album Mule Variations took the sonic weirdness of Bone Machine and combined it with downtrodden, bluesy ballads of his earlier work, creating an album that is much more approachable to the uninitiated.