This was an issue in Skyrim, where if your armor was too high, or your weapon too strong, the game no longer considers anything a threat and would therefore not queue the combat music. This is a pretty big issue for those of you with custom combat music mods.
Instructions:
Drop music.txt into your install directory (Not the data folder, just the Fallout 4 folder)
Type in your Fallout4.ini under general:
sStartingConsoleCommand=bat music
folder is located in My games/Fallout4.
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Added an .esp for those of you that prefer that method.
Drop into your install directory.
Thanks to chiknnwatrmln
For the .esp and the assistance.