Over on youtube, Silen founder Adam Fligsten breaks down the primary ways that almost every video game sequences music.
Vertical and Horizontal resequencing might sound like confusing subjects, but they are just making decisions about how and when music is playing.
(also called “hamburger” while learning)
The concept with vertical sequencing is setting up your tracks so they are stacked on top of each other, and the volume of the tracks changes based on what is happening in the game. The key to this is that the files will sound good in most places if they fade into each other.
Often these are different stems or components of the same song, but not always; some games have found creative ways of doing vertical resequencing with completely different songs.
(also called “railroad” while learning)
The content of horizontal sequencing is setting up your tracks so that they will trigger one after another. There is often a little bit of overlap as a new track begins and the old track ends. Each track is connected, one after another (like a train!)
This can be entirely different songs or very short segments of the same song. There usually aren’t multiple tracks playing simultaneously (except for the overlap during transitions).
Most games do some version of both of these techniques, switching between them when it makes more sense for a game. You could have a longer moment in a game with a big Vertical section, which then gets connected to shorter horizontal moments. There is no right way to do it, but different gameplay will work better with different techniques.