In the series "composers cannot hide anything from Hrollo".
Listen to the first 10 seconds of that track:
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(It's the main theme of the soundtrack of a 1980 supernatural horror film called "Inferno")
Ok? Now listen to the first 12 seconds of this track:
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(It is the second-to-last piece of Mussorgsky's suite "Pictures at an Exhibition")
Coincidence? How about this: "Inferno" is part of a trilogy of film about the "Three Mothers", a trio of evil witch-sisters.
This particular piece of Mussorgsky references Baba Yaga, a witch from Russian folklore… which is sometimes depicted as three sisters.