TITLE – many of Cage's titles are self-explanatory (such as Nocturne), or involve NUMBERS.  Others elide two words, such as Mureau (music/Thoreau) and Whiskus (whistlin/hauku – linking the first word of the source text (from which the MESOSTIC is derived) with the haiku-like series of short poems which resulted).  The Six Melodies are indeed melodies, six single lines split between the two instruments (although some single notes in those lines are made up of two or more pitches).