The Beta Placeholder Music applicable to the full release.
Before the proper music composed by Ian Livingstone was implemented, the game used music composed by Andy Blythe & Marten Joustra from Haven Call of the King, a previous TT title, as placeholders. The selection was very limited, so to make up for the small amount of placeholders vs the amount of tracks in the final game, variations altering the pitch and tempo have been made to better vary the music even if not by much. As a result among other factors, this is not 100% reflective of what this would have sounded like at the point in development in which these were used.
It's as simple as placing the folder into its respective place in your Bionicle Heroes folder of choice, of course making sure to back up your original files first.