Every area has a very different musical theme. The music changes depending on the time of day, specifically, during most of the day, the normal tune plays. But once the lights start to fade, and it's time to round up all Pikmin, the music changes to a calmer mood of what it once was.
On Challenge Mode, the music that normally plays for the current level is sped up, as well as the darker remix noted above.
Sometimes, when near an enemy creature, more percussion and occasional brass are added to the song. This is a good way to notice that you could be in danger. A great example of the music change is in the Distant Spring.
The soundtrack for Pikmin is called Pikmin Worlds.
Pikmin 2 features distinctive music in both the overworld areas and caves. Music in caves is often minimalistic and appears to be chosen according to the difficulty and kind of hazards and beasts that await the Pikmin and Captains. In rest areas, a recognizable soft melody plays.
Music in Pikmin 2 plays as a number of different variations depending on a few variable factors. It varies when Pikmin interfere with beasts or when they carry a treasure, for example; and the tempo decreases as the active Captain loses life. When either Louie or the President is the active Captain, the music often has a time signature of 6/8 or 9/8, instead of 3/4 or 4/4 with Olimar. Above ground, the music also changes depending on the time of the day, much like in the first Pikmin game.
For the advertising of Pikmin 2, another song from Strawberry Flower, Tane no Uta, was used.
Pikmin 3's music goes for having a more natural, simple, but atmospheric affect rather than having melodically strong tunes.
Every area in Pikmin 3 has a total of 6 music variations: Morning, Morning Work, Work, Afternoon, Evening, and Weather. The "Weather" variation is shared by all the regions except the Formidable Oak and the Distant Tundra, which have their own unique themes when Weather is active. All cave areas share the same soundtrack.
Unlike in the past two games, Pikmin 3 does not have an extra variant of each song that changes when an enemy is nearby. Instead, a continuous tampani and cowbell beat is overlayed with the normal music to signify enemies in the vicinity. Pikmin 3 does, however, have unique music variants for when Pikmin are preforming tasks such are building bridges or carrying spoils.
For every official trailer of the game, Mission Mode's main theme was used.