The music of Filosofem continued Vikernes' experimentation with minimalism, repetition, and ambient music within black metal. The tracks are all quite long (the shortest being just over seven minutes), and are typically composed around very few musical motifs. For instance, "Jesu dod", a track of over eight-and-a-half minutes, is primarily based around variations of a single riff. "Burzum", the opening track, features a prominent melody played by a synthesizer, and the two "Decrepitude" tracks consist of sound effects over very sparse guitars. The album also included Burzum's longest ambient track to date, the 25-minute-long "Rundtgaing av den transcendentale egenhetens stotte". The album cover and booklet contain artwork by Theodor Kittelsen. The front cover is named Op under Fjeldet toner en Lur (Norwegian for "up under the mountains a clarion call rings out").
