Mogwai Fear Satan is a long guitar-based instrumental, using basic rock instrumentation; guitars, bass, and drums, along with flute that begins with a guitar melody played by Stuart Braithwaite and John Cummings, which is soon joined by bass played by Dominic Aitchison and a frantic drumbeat played by Martin Bulloch, which fades gradually in. The same guitar melody is repeated throughout the song; at times almost frighteningly distorted. During the quiet parts of the song, in the build up to the explosion of sonic noise and feedback which Mogwai are known for, there is a quiet haunting flute melody played by Shona Brown over tribal-sounding drums. The song slowly fades out into feedback and noise.

It is a fan favourite and a regular part of Mogwai set lists, often being played as a show-closer or an encore. When it is played live, Mogwai make use of an extreme contrast between quiet and loud, going from playing almost nothing, to blinding and deafening the audience with a huge explosion of light and noise. The origin of the song title stems from bassist Dominic Aitchison’s fear of the Devil, due to his Catholic upbringing, which continues to this day as Aitchison is the only religious member of Mogwai.