Fallen was recorded and mixed during two weeks in Grieghallen studios, using a Spector bass with alembic electronics on a VOX AC50 amp from 1965, a Ludwig drum kit (with a 26 inch kick) from 1975, a Neumann M149 microphone and stereo Schoeps CMTS 501 U microphones for vocals, an OBH Nordica Harmony 6487, a custom Stig instrument and a Peavey 23 guitar on a Peavey 6505 (120 Watt) amp.
According to Varg Vikernes himself, "Musically Fallen is like a cross between Belus and something new, inspired more by the début album and Det som engang var than by Hvis lyset tar oss or Filosofem. The sound is more dynamic – we mastered the album as if it was classical music – and I was more experimental than I was on Belus in all respects. Lyricwise it is similar to the début album, in the way that it is more personal and focuses on existential issues, but the mythological undertone known from Belus is still there. I have also included some ambient tracks – a short introduction and a longer conclusion".