According to this article, people tend to speak in tones that reflect their musical backgrounds.
http://www.nature.com/nsu/010524/010524-2.html
And apparently,we are more musical when shouting. Napsterite flame wars must be positively operatic!
This study indicates that pianists accentuate melody by playing certain notes louder, and hence earlier, than others.
http://www.nature.com/nsu/010719/010719-17.html