Peaks is the default music theme of Jill Goes Underground which plays in the main menu but also can be heard in several levels.
The title comes from the file name, but Dan Froelich explained that the file names were in fact the proper full titles. The file in the game folder is named PEAKS.DDT.
Jill of the Jungle: Jill Goes Underground (DOS)
In second game in the series Peaks can be heard in the Main menu, Un-named level 0 (top-left screenshot), "The Land Of Eternal Weirdness" (level 15; top-right screenshot), ending part of "Think Fast" (level 19; bottom-left screenshot) and during the ending sequence (bottom-right screenshot).