The most difficult problem in answering the question of how music creates emotions is likely to be the fact that assignments of musical elements and emotions can never be defined clearly. The solution of this problem is the Theory of Musical Equilibration. It says that music can't convey any emotion at all, but merely volitional processes, the music listener identifies with.Then in the process of identifying the volitional processes are colored with emotions. The same happens when we watch an exciting film and identify with the volitional processes of our favorite figures. Here, too, just the process of identification generates emotions.
An example: If you perceive a major chord, you normally identify with the will "Yes, I want to...". If you perceive a minor chord, you identify normally with the will "I don't want any more...". If you play the minor chord softly, you connect the will "I don't want any more..." with a feeling of sadness. If you play the minor chord loudly, you connect the same will with a feeling of rage. You distinguish in the same way as you would distinguish, if someone would say the words "I don't want anymore..." the first time softly and the second time loudly.
Because this detour of emotions via volitional processes was not detected, also all music psychological and neurological experiments, to answer the question of the origin of the emotions in the music, failed.
But how music can convey volitional processes? These volitional processes have something to do with the phenomena which early music theorists called "lead", "leading tone" or "striving effects". If we reverse this musical phenomena in imagination into its opposite (not the sound wants to change - but the listener identifies with a will not to change the sound) we have found the contents of will, the music listener identifies with. In practice, everything becomes a bit more complicated, so that even more sophisticated volitional processes can be represented musically.
Further information is available via the free download of the e-book "Music and Emotion - Research on the Theory of Musical Equilibration:
or on the online journal EUNOMIOS: