The Fly-By-Night Fright Club is a nightclub owned by Ghostwriter that is located within the chasm of a mountain in the cartoon show episode "Harmony Steals The Show". It is where Ghostwriter lives and supposedly "composes" his own music, but mostly it is used for entertaining his ghostly patrons with spirit acts.
In the episode, the patrons are getting bored with the acts that they have seen for enough lifetimes and are starting to demand for "live entertainment". In his search for "live entertainment", Ghostwriter sees Harmony trying to compose his own symphony and offers him a completed original symphony that he can claim as his own in exchange for signing a contract, which Harmony signed without reading that it would bind him as Ghostwriter's eternal "live entertainer".
When Papa Smurf found out about where Harmony received the symphony that he claimed to have composed, he and his little Smurfs went to the nightclub to confront Ghostwriter to have him set Harmony free. Ghostwriter responded by having Harmony be put on trial by a spectral judge and a jury of deceased composers to determine whether Harmony should be set free from his contract. Papa Smurf and his little Smurfs played out the entire symphony that Ghostwriter claimed was his own original work, and it was revealed that the whole work was a plagiarism of various works by other composers. The judge deemed Ghostwriter guilty of perjury and thus had him taken away while Harmony was set free and released into Papa Smurf's custody.