Custom soundtracks?

I'm going to assume your making an offline game, and you want players to load custom tracks from their Hard drive;

System.IO will allow the user to setup a folder for the music, OGG files are recommended since unity has an encoder for them. You need to tell unity to load those files when the user wants them.

the easiest way for you would to have a folder in your build directory with the .ogg files in them. then you need to set up your game so that it will play those files based on the names of the files e.g Title.ogg will play at your title scene, Cursor.ogg will play when you click on somet$$anonymous$$ng.

if making a web game, w$$anonymous$$ch you didn't specify... you only mentioned wikipedia. it won't be much different, but the file will need to be uploaded on a server or somet$$anonymous$$ng. or you could try streaming it.

Maybe edit the HTML to autoplay a music file on your server, so then it plays anytime goes on your game page...

If not that, you can do music/audio in game.