Grave Composer module
.wow files are modules produced by Grave Composer / Mod's Grave for the IBM (presumably MS-DOS). They are a variation on the standard 8-channel Amiga Module, but use the "M.K." identifier rather than "8CHN" (see Amiga Module for more information). They can potentially be identified in two ways - by the file extension (probably not the most accurate method) or by calculating the size of the module for 8 channels and comparing this to the actual module length (see the linked document for the appropriate calculation). Probably using both of these methods together is the best way to identify modules in this format.