I have just watched the trailer for Christopher Nolan’s film, Dunkirk (2017):

I was particularly taken with the sound design.  In the first half there are low drone sounds that I suspect were created from aircraft dive sounds.  IMO these create a feeling of impending doom and dread that reinforces the trapped feeling.  Then in the second half the action is supported by a heart-beat that for me went with a feeling of survival.  It’s my hunch that these are the main narrative drivers for the film, but both of the sounds were very much larger than life and not very subtle, but worked brilliantly in the context of a trailer, where the themes need to be delivered in a short space of time.  It will be interesting if these sounds are actually in the final film and if they are will they be in the same form?

I’ve never done any trailer work and I have heard that there are agencies that specialise in just doing film trailers.  Does anyone have any experience with sound design for trailers?  Are there any particular strategies or techniques that are employed?