Harmony is a 11-level stand-alone total conversion, created by Thomas van der Velden (t.v.) and released after five years of development. In its updated 1.1 version, it is recognized as an IWAD by ZDoom 2.4.0 and newer. The soundtrack consists of three songs from Kyū's album "The Edge" (2009), specifically track #6 ("Untitled", used on MAP02, MAP03, MAP10 and MAP11), #7 ("Mercury Stripes, Blue Mess", used on MAP01, MAP04, MAP05, MAP08 and MAP09) and #10 ("The Edge", used on MAP06, MAP07, and the intermission, endgame and title screens). James Paddock (Jimmy) later created an optional MIDI pack providing a new, original soundtrack composed specifically for Harmony.