"Music is a higher revelation than all wisdom and philosophy." -------Ludwig van Beethoven
"Information is not knowledge. Knowledge is not wisdom. Wisdom is not truth. Truth is not beauty. Beauty is not love. Love is not music. Music is the best..." --------Frank Zappa
To answer this question, I can't help but to talk about music in general first. Music brings you into a zone where you can just "be", where it is the situation of "truth" when words and thinking mistake you often. Music brings out your emotion all at once where anger is safe, sadness is comfort, arguement is harmony, war is peace......
Now back to your question: How piano music effects people? Unlike string instruments that there is always tunning and intonation issues, piano is the kind of instrument that you can make "correct" sound when you play. When I say "correct", I simple just mean "in tune" if the instrument is tuned well. For some people, piano music is soothing and calming, for some people, piano music can be percussive and exciting.
Please visit the site where there is sample of my performance at http://www.webconcerthall.com/archive/artist/piano...
and my website at http://helenlinpiano.weebly.com/