Change of Genre

I was originally planning of producing a psychological thriller. However, now I have thought of a location and a narrative for my teaser trailer, I believe it would be more relatable to a horror genre.  My initial ideas for my trailer would be having one young girl in the forest, looking ghostly, singing a nursery rhyme, as nursery rhymes are iconic of childhood. So using a child would be more effective than using a teenage or middle aged actress. I want to have the girl singing a nursery rhyme. For example, at the moment I am thinking 'Jack and Gill' so when the girl sings in a creepy, whispering voice 'Jack fell (pause) Down.' It feels more dramatic and is emphasised when it cuts to people in the forest struggling (falling) down in danger. After the ghost girl has sang each line, it cuts from the girl to action in the forest. The action is unexplained as the conventions of all teaser trailers are to with hold information and keep the audience engaged.