You ever thought, what is the "CampaignTracks" Folder? and What are these tracks? They are all the Tracks in the Championship, you can customize 'em, but you can also, collect 21 of your custom tracks,rename them and replace/put on the CampaignTracks Folder.
Go to the last level of the championship.
when the race starts go back to the menu, play a city race:
The City Will have people looking at you, and a great new music, (the music appears in all types of stages)
BTW A GLITCH!
When you do that DON'T even go at Construction or the game crashes!
To build you need to leave game and start again.