The two decade struggle for Brahms to create a symphony is legendary. He was understandably stressed by the inevitable comparison that would be made to Beethoven's symphonies. And we all hear the many Beethoven references that abound in the Brahms first symphony. But no one mentions equally clear references to the music of Wagner, particularly Tristan und Isolde. Brahms was equally obsessed/fascinated with Wagner's harmonic innovations and the Tristan progression really forms the core idea in his first symphony. But unlike Wagner who uses these progressions to create a labyrinth that wander to the point of losing a sense of tonal center, Brahms gives these same progressions a "Beethovenian" sense of purpose, continually emphasizing the dominant of the tonal center of the piece.