The songs are triggered to play based off when players enter a specific cell-- currently only the base game is supported. However, you can easily add any additional cells you'd like to the mod by adding them in the "MS_c_Daedric.json" file in the MWSE>config>MS folder.
For those using a patched Tamriel Rebuilt and Morrowind Rebirth (because I do not know for sure which one is adding which enemies) you can add these to MS_e_Daedric.json:
"Dremora Lord of Inspiration", "Dremora Lord of Terror", "Dremora Lord of Divinity", "Dremora Archer", "Dremora Varlet", "Dremora Churl", "Dremora Caitiff", "Dremora Kynval", "Dremora Kynreeve", "Dremora Kynmarcher", "Dremora Markynaz", "Dremora Valkynaz", "Silver Saint", "Fire Monarch", "Frost Monarch", "Storm Monarch", "Earth Atronach", "Xivilai", "Seducer", "Vermai", "Lord Drekhva Yashaz", "Uridimmu", "Dridrea", "Dridrea Matriarch", "Dridrea Monarch", "Dridrea Spawnling", "Guardian", "Vermai Vault Guardian"
and to MS_c_Daedric.json for Tamriel Rebuilt daedric ruins, add:
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"Dremora Lord of Inspiration",
"Dremora Lord of Terror",
"Dremora Lord of Divinity",
"Dremora Archer",
"Dremora Varlet",
"Dremora Churl",
"Dremora Caitiff",
"Dremora Kynval",
"Dremora Kynreeve",
"Dremora Kynmarcher",
"Dremora Markynaz",
"Dremora Valkynaz",
"Silver Saint",
"Fire Monarch",
"Frost Monarch",
"Storm Monarch",
"Earth Atronach",
"Xivilai",
"Seducer",
"Vermai",
"Lord Drekhva Yashaz",
"Uridimmu",
"Dridrea",
"Dridrea Matriarch",
"Dridrea Monarch",
"Dridrea Spawnling",
"Guardian",
"Vermai Vault Guardian"
and to MS_c_Daedric.json for Tamriel Rebuilt daedric ruins, add:
"Ald Balaal",
"Ald Mirathi",
"Ald Niripal",
"Ald Uman",
"Ald Uran",
"Anashbibi",
"Ashinanibibi",
"Ashpibishal",
"Ashushushi",
"Baelkashpiu",
"Bal Dushal",
"Balititashpi",
"Bapatipi",
"Boethian Deeps",
"Bushipananit",
"Ebamusharisus",
"Ebunammidan",
"Emmurbalpitu",
"Essarnartes",
"Esuranamit",
"Hadrumnibibi",
"Hummurushtapi",
"Ibiammusasashan",
"Ikinammassu",
"Kannidamarus",
"Malkamalit",
"Mashadananit",
"Narasnabad",
"Onimushili",
"Ossurnashalit",
"Rasdamassilu",
"Shambalu",
"Sirsadrorran",
"Teknilashashulpi",
"Ulanababia",
"Veranzaris",
"Yabananit",
"Yamandalkal",
"Yamuninisharn",
"Yanishanabi",
"Yashazmus",
"Zalitalan",
"Zatamushi"