Jesper Kyd composed the main music for the original Assassin's Creed game.
Kyd, a Danish composer known for electronic and orchestral game scores, wrote the soundtrack for the 2007 title. His music combines choral textures, orchestral writing, and electronic sounds to support the game's medieval settings and modern science-fiction framework.
The score helped establish the series' recognizable musical identity, especially through its use of atmosphere during exploration, investigation, and assassination missions. Kyd later returned to compose music for Assassin's Creed II, Assassin's Creed Brotherhood, and Assassin's Creed Revelations.
The franchise subsequently used other composers, including Lorne Balfe, Sarah Schachner, and Jesper Kyd himself on later projects. Those credits can cause confusion when a question asks specifically about the original game's main theme rather than the series as a whole.