The use of pre-existing music is, first of all, surrounded and conditioned by particular production contexts and considerations. The use of pre-existing music is also viewed commercially and critically, by those in and around the film and music industries, as a distinct practice connected to distinct risks and possibilities. Pre-existing music is often expected to be 'clever', but it is also commonly ambiguous, opening films up to readings that diverge strikingly from both authorial intention and each other. Pre-existing music is, uniquely, music changed by its filmic appropriation; music with both a 'before' and 'after' in the public sphere. Video games can differ substantially from media texts of other types in their uses of music, because of their interactive nature. A quest for perfection in Guitar Hero and similar music games will normally require several attempts at each individual track, and the potential for repetition is multiplied by the game's inclusion of varying difficulty levels.