Variety has posted an interesting article on the basics and trends of trailer music. It features quotes from several editors, music supervisors, and production libraries. Thought it was worth sharing.
Trailers for big, glossy tentpole movies typically deliver a booming symphonic score or operatic choral sounds to convey an epic feeling, though the downside to such larger-than-life bombast is the ring of overfamiliarity. The teaser trailer for "Battle: Los Angeles," on the other hand, broke with convention by using the sparse, eerie tune "The Sun's Gone Dim and the Sky's Turned Black" from techno musician Johann Johannsson that played over wordless human action. It's among the nominees for a Golden Trailer award.