Final answer:
Symphonie fantastique, composed by Hector Berlioz, is innovative for its story-telling programmatic structure, the use of ideée fixe, and its expanded orchestration with novel instrumental effects.
Step-by-step explanation:
One innovative aspect of Hector Berlioz's Symphonie fantastique is its programmatic structure, which tells a story through music, a concept that was revolutionary at the time of its composition in 1830. The symphony employs a technique known as ideée fixe, a recurring theme that represents the protagonist's beloved, transforming throughout the piece to reflect the story's changing emotions and scenarios.
Additionally, Berlioz's use of a large and varied orchestra, including expanded percussion and novel instrumental effects, like the use of col legno in strings (playing with the wood of the bow), was groundbreaking and contributed to the symphony's vivid storytelling.