Toy Story Mash-up not playing custom music (in world)

The Toy Story Mash-up purchasable from the Store includes custom music from the Toy Story franchise. This custom music is supposed to play in the world and in the main menu when the resource pack is on. When in the world, the custom music does not play and plays the vanilla music. I assume this is a problem with biome-dependent music as the custom music works fine in the main menu.