You can listen to the main theme from the National Symphony Orchestra or read more about its structure on Billboard and Wookieepedia .
Composed by John Williams for the 1977 film Star Wars: Episode IV – A New Hope , the Star Wars Main Title is a iconic, brass-heavy, B-flat major symphonic march. It is celebrated for its heroic, ternary-structured composition that brought classical, leitmotif-driven scoring back to blockbuster cinema. Star Wars Main Theme (Full)