Music for the Animatic/trailer

By analysing other trailers, as a group we have concluded that the music for the trailers, can often include "popular" music at the opening 30-40 seconds to establish the trailer, then go into the 'eerie and creepy' type of music later on. For the animatic and trailer will possibly vary, for example, music in the trailer has to be copyright free, however, in the animatic we can use copyrighted music, as an EXAMPLE of the genre/style that will be used in the real thing, there will be 2/3 soundtracks  one snippet of dance/chart music at the start where the trailer is established (uni students living a normal life partying) then one or two snippets of music, possibly classical in a minor key, to show signs of horror.