A soundtrack can be very useful for setting the scene. The style of music tells you what the mood's going to be, and awesome moments need booming soundtracks with lots of instruments making up the sound to be even more awesome. But with depressing moments, it's the other way around: you only need a slow and soft melody with very few instruments to know that what's happening or has just happened is supposed to be a Tear Jerker - if not for the audience, then for the characters at least. Subtropes include Nostalgic Music Box, Lonely Piano Piece, Playing the Heart Strings and One-Woman Wail.