Have there been any scientific studies into the emotional content and significance of music?
I can only (wildly) theorise that there is a form of resonance at play.
Wave-particle duality states that all matter can be modelled as waves, and vice versa. Air pressure can affect our bodies in various powerful ways, if not as obviously as the brown note. This is not to say there is a definite solid link anywhere; but my theory is that music intersects with the brain on a fundamental level.
Your sense of hearing, even more than sight, is hardwired into your subconscious, to the 'animal' centre of your brain to provide early warning, fight-or-flight responses to external stimuli without the time-lag required for complex reasoning. When we listen to music that suits our mood in tempo, chords and individual notes, this becomes imprinted upon our brain as the sound of that moment - especially if the moment is associated with a strong emotion, love, happiness, or stupidity - it becomes the 'warning' of that moment - a more enjoyable parallel to the sound of a big frikkin bear approaching through the woods. The same can be said for negative emotions, which is why I will become violent if anyone plays 'lick it' or similar tunes to me.
This also gives proviso for music not suiting your mood - the waveform of the music is a discord with your internal patterns, distorting and undermining your thoughts, causing you to wish to switch it off.
Finally, it explains why 'The Rip' feels like heroin might to me just now.