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 Monkeyd 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.
iMUSE on Wikipedia