The type of music used in a trailer is often one of the primary indications of genre. Listen to the musical clips below and try to distinguish what type of film they came from.
Action
Drama
Comedy
Thriller
Action
Action
Drama
Drama
Comedy
Comedy
Thriller
The mood of the music signifies the mood of the film in the trailer just as it would do in the film itself. As this is the case, it is often quite easy to tell the genre of a trailer just by listening to its music.
Thriller

A film's trailer can also serve to advertise the soundtrack album for a film, an ancillary market that has taken off dramatically in the 1990s. If a song from a films hits the number one slot its video, including of course clips from the film itself, will be shown everywhere. Three of the longest stints at the UK number one slot have come from film themes, Bryan Adams' "Everything I do, I do it for you" (Robin Hood: Prince of Thieves), Wet Wet Wet's "Love is all around" (Four Weddings and a Funeral) and Whitney Houston's "I will always love you" (The Bodyguard) coming in at 16, 15 and 14 weeks respectively.

The trailer for the 1996 Michelle Pfeiffer film Dangerous Minds used it's theme song "Gangsta's Paradise" to its full extent. Using no soundbites or voiceovers the entire trailer is a series of images set to music. The distinction between a trailer and a music video becomes ever more hazy as it becomes difficult to tell which aspect of the trailer, the film or the song, is trying to be sold the most.