iMUSE (stands for Interactive MUsic Streaming Engine) is a game engine specifically designed to synchronize music with visual action in a video game. The point of iMUSE is to dynamically make the music fit to the scenes, characters and moods of the game, much like a movie soundtrack. It is patented under US Patent No. 5,315,057 by LucasArts. It was added to the SCUMM engine in 1991.
The first game to use the iMUSE system was Monkey Island 2: LeChuck's Revenge and it has been used in all LucasArts adventure games since. It has also been used for some non-adventure Star Wars related LucasArts titles such as Star Wars: X-Wing, Star Wars: TIE Fighter, Star Wars: Dark Forces and Star Wars: X-Wing Alliance.
Philosophy and techniqueEdit
A typical example is in the flight engine of X-Wing: While the player is flying, the engine plays the normal soundtrack, loosely based on Star Wars theme. When a Rebellion or Imperial craft enters the area, the music is interrupted and the brief 'Rebellion theme' or The Imperial March cue is heard.
Other cues contribute when a mission objective is reached or failed, when the player Hyperspaces back from a successful mission, or a failed mission etc.
The interruption of music, insertion of short cues and continuing of the music, uses a sophisticated algorithm which makes a smooth and almost unnoticeable transition. The result is heard like a unique, flowing piece, with its own variations that match the story.