Version 1.1 was a critical technical update for the WAD file. The original v1.0 release suffered from a major bug where the music was improperly mapped, causing tracks to play on the wrong levels or not at all.
hexdd.wad v1.1 was created using the Doom Construction Kit (DCK), a popular tool for building and editing WAD files. hexen, the creator of hexdd.wad, was an experienced mapper and game designer who had already made a name for himself in the Doom community. His inspiration for hexdd.wad v1.1 came from various sources, including classic horror movies, sci-fi literature, and, of course, the Doom game itself. hexdd.wad v1.1
If you want, I can: (a) produce a sample README and changelog lumps formatted for inclusion in the WAD, or (b) produce a step-by-step wadinfo/SLADE inspection script. Which do you want? Version 1