Somebody has to be in charge of finding the next Michael Jackson, and that somebody in music publishing is known as a talent acquisition exec. A role parallel to that of an A&R exec for a record label, a talent acquisition exec is in charge of finding undiscovered musical talent. These people seek out promising talent, sign them and foster their careers, offering advice in terms of songwriting, live performance, recording and publicity. They are also in charge of acquiring both old and new publishing rights.
An amateur songwriter's song might find its way onto the next Miley Cyrus album thanks to a song plugger. Song pluggers are in the business of pitching songs. The traditional song plugger offers demos by songwriters as potential songs for artists to record. For example, "Like a Virgin" was written by songwriting duo Billy Steinberg and Tom Kelly and was offered to Madonna to record. More recently, song pluggers are often responsible for promoting songs to get into television and movies.
You can hear Bob Dylan's "The Man in Me" in the movie "The Big Lebowski" or on the radio, thanks to licensing professionals. The licensing department in music publishing works with television, movies, record labels and other outlets to allow usage of songs in their publishing catalog. They develop relationships with these professionals, setting fees and closing deals.
Imagine how much money Led Zeppelin members have made off of "Stairway to Heaven." They can thank those working in the royalty department for receiving all the money that is owed to them. The royalty department works with performing rights organizations such as ASCAP and BMI, who monitor every instance in which a song is played. The royalty department then distributes these royalties to songwriters and artists or other copyright holders.