The Rest of the World Show is broadcast on Friday mornings between 9:30 and 11:00 (London time). The original concept was that the music played would be from countries other than the United Kingdom and the United States of America.
We immediately broke this rule by playing a song in Welsh in the pilot. So the first new rule was that music from UK or USA was OK providing it was in another language.
Subsequently, another rule is in place to allow any UK/US music that features in the WMCE world music charts. Sam Lee is a classic example.