A secret or indirect payment (as to a disc jockey) for a commercial favor (as for promoting a particular record). The history of payola is well documented in the book "The Hitmen", by Fredric Dannen. 

Warner Music Group Corp. has agreed to pay $5 million to settle an investigation into payoffs for radio airplay of artists, New York Attorney General Eliot Spitzer said Tuesday.

Warner is the second major recording company to reform and settle with Spitzer in a practice the attorney general said was "pervasive." In July, Sony BMG Music Entertainment agreed to pay $10 million and stop bribing radio stations to feature artists.