What is the stairway to heaven rule?

The "Stairway to Heaven" rule refers to a legal standard used in U.S. copyright law, particularly in cases involving music. It originates from the lawsuit over the song "Stairway to Heaven" by Led Zeppelin, where the court examined whether the song infringed on another's work. The rule emphasizes the need for substantial similarity in both the musical composition and the expression of ideas, not just the presence of similar elements. Courts typically assess whether an average listener would recognize the similarities, thereby influencing how copyright infringement cases are evaluated.