 Ghosts I – IV is the sixth studio album by American industrial rock band Nine Inch Nails , released on March 2 , 2008 . The team behind the project included Nine Inch Nails front man Trent Reznor , studio @-@ collaborators Atticus Ross and Alan Moulder , and instrumental contributions from Alessandro Cortini , Adrian Belew , and Brian Viglione . Reznor described the music of Ghosts as " a soundtrack for daydreams " , a sentiment echoed by many critics who compared it with the work of Brian Eno and Robert Fripp . The songs are unnamed , and are identified only by their track listing and group number . 
