Complex sentence: The release of "Mirage" was a key event in an ongoing controversy over payola, the alleged practice of a record label paying money to radio stations to have them play a song without the listener knowing that the station has been paid to play it.
Split into simpler sentences: The release of "Mirage" was a key event in an ongoing controversy over payola. Payola is the alleged practice of a record label paying money to radio stations to have them play a song without the listener knowing that the station has been paid to play it.