Simplify the following text for a Grade 11 native English-speaking person.
Original: The duo came back in 1998 recording their materials based on what the demand was in central European music markets at the time in the late 1990s , which required their original 1980s mellow Europop sound to switch into 1990s up-tempo Eurodance .
Simplified: To accommodate central European music markets of the late 1990s , they changed their original 1980s mellow Europop sound to an up-tempo Eurodance .