A few years ago I read about a frequency content view of emotional music. In general they found that the high frequency content increased as emotional songs/pieces progress. It was true is all genres studied. One example that they analyzed in depth was Queen's Bohemian Rhapsody.
Something to consider is that most instruments have more overtones at ff than at pp, so just starting out quiet and ending up loud will do the trick. But you can also add more flutes, cymbals, glock as the piece goes on, and play things in higher registers to get this effect too.