Music
The composer of both Pikmin and Pikmin 2's music is Hajime Wakai.
Pikmin
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 darker remix 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, some extra beats 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.
Strawberry Flower released a Pikmin-themed song, Ai No Uta, along with the release of Pikmin, and later a number of other Pikmin-themed singles and albums.
Pikmin 2
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 is not as regualar as 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.