I think Dave Marsh's book (which I don't have here) mentions that Entwistle's album "Rigor Mortis Sets In" had to be changed to "John Entwistle's Rigor Mortis Sets In" because there was already a band by the name of Rigor Mortis in the U.S. My guess is the album you mentioned is the "other" Rigor Mortis.. Wes