Banjo-Kazooie has four unused tracks left over from the Beta version of the game. It is theorized that "Advent" was supposed to be used for a cut level of the game, Fungus Forest, which became the Fungi Forest level in Donkey Kong 64. There are also two unused versions of the Click Clock Woods theme and an unused Mumbo Jumbo song called "Mumbo's Raindance".
Source: Banjordan's BK Lair
USF Source: USF Central