Horizontal resequencing
Also said as Branching music, Music states, Transition on the bar
Cutting music into sections and letting the game choose which plays next. Requests wait for a musically sensible point, usually the next bar line, so changes sound written.
It allows real changes of melody and key, which layers cannot do. The cost is delay: the music may need a second or two to answer, so it cannot mark a split-second event.
Say it
“When combat starts, change to the fight section on the next bar line, at most 2.4 s later. Play a stinger on the next beat to cover the wait.”
Where you’ve seen it
Monkey Island 2, the first game to use LucasArts' iMUSE system by Michael Land and Peter McConnell. In the town of Woodtick each building plays a variation of the theme on a different instrument, and leaving ends on a closing flourish back into the main theme. Earlier games could only fade or cut.
Not to be confused with crossfade
A crossfade blends two tracks whenever it is told to, whether or not they fit. Resequencing waits for a moment when they do.