Sorry I've come late to this topic and I haven't read all the replies inbetween, but putting the emotion into the music is quite a complex issue. Firstly you have to have the technique and control over your unstrument to be able to express nuances in quite delicate detail. You also need some understanding of harmonic progression and phrase structure - the high and low points, plus where the melody is headed, etc. That's just the technical aspect!!! To add the emotion, especially if the piece doesn't already have a descriptive title, but in some cases, even if it does, I try to think of a character (imaginary or real/fictional etc) or a scene from a film (again, sometimes I create my own, sometimes I work from films I've seen .........) and then try to convey that through the music by creating a very strong mental image in my head and trying to convey it in how I express the music. Jaws has featured in one piece - and The Lord of the Rings gave me quite a few snippets and scenes/characters to work from too!!!!