Classic videogame by Capcom mixed with the music of one of the most radical composers of the XXth century - Galina Ustvolskaya.
The soundtrack is her Piano Sonata No.6 performed using chiptune 8bit sound.
The result fits the atmosphere of the game pretty well.
Actually, both the composer and the main hero of the game share a common enemy. They spend their life fighting the evil forces and Lucifer himself (Ustvolskaya was very religious and definitely believed that her music can be a weapon against this powerful foe).