http://en.wikipedia.org/wiki/Song-plugger
A song plugger or song demonstrator was a vocalist or piano player employed by department and music stores and song publishers in the early 20th century to promote and help sell new sheet music, which is how hits were advertised before quality recordings were widely available. Music publisher Frank Harding has been credited with innovating the sales method. Typically, the pianist sat on the mezzanine level of a store and played whatever music was sent up to him by the clerk of the store selling the sheet music. Patrons could select any title, have it delivered to the song plugger, and get a preview of the tune before buying it.
Although the terms are often used interchangeably, those who worked in department and music stores were most often known as “song demonstrators”, while those who worked directly for music publishers were called “song pluggers.”
Musicians and composers who had worked as song pluggers included George Gershwin, Ron Roker, Jerome Kern and Lil Hardin Armstrong.
Later, the term was used to describe individuals who would pitch new music to performers, with The New York Times describing such examples as Freddy Bienstock performing a job in which he was “pitching new material to bandleaders and singers”. In 1952 Ernest Havemann wrote:
There are about 600 song-pluggers in the U.S.; they have their own union; they are powerful enough to bar all outsiders; and they command fees up to $35,000 a year (worth $307,675 today) plus unlimited expense accounts. Their job is to persuade the record companies to use songs, put out by their publishing houses, and the radio station disk jockeys to play the records.”
Song plugging remains an important part of the industry. Record labels and managers will actively search for songs that their artist can record, release and perform, especially those who don’t write their own material.
[So, how can this be a ‘scam’ – Watch out for those song pluggers who want to charge you an up-front fee to allegedly push your song to an artist. An honest song plugger will not charge you as they will make money when and if your song gets chosen by an artist to be on his/her record.]