Final answer:
Bernard Herrmann established his reputation with his score for Citizen Kane (1941), demonstrating his skill in enhancing storytelling through music.
Step-by-step explanation:
The musician who established his reputation with his stunning score for Orson Welles's film Citizen Kane (1941) is Bernard Herrmann. Herrmann was an American composer known for his work in film music, particularly with director Orson Welles but also with director Alfred Hitchcock in later years. He was notable for his ability to use music to enhance the storytelling experience, and his score for Citizen Kane is considered a masterclass in film scoring.