Pokemon Style Sound Fade...

Bare with me on this one...

Okay - I want to be able to fade a music track at any time so that it fades in and starts with another music track in Unity at a certain point (for example when close to a box or another object)

The reason I mentioned Pokemon is because the games do exactly what I want to recreate in Unity when the player moves from town to town or route to route. They fade out at any point when the user moves to another area and start another music track when the player enters a different location.

Any ideas how I could recreate that in Unity? If you have any suggestions I'd love to hear them.

For the sake of demo codes that anybody might drop here to let me know I'll call the two tracks I want to use:

MusicTrack1.mp3

and

MusicTrack2.mp3

Thanks for you help in advance! :D