The music we sing on Sunday's is sacred because it's an expression of our faith. The Lord revealed to Joseph Smith "For my soul delighteth in the song of the heart; yea, the song of the righteous is a prayer unto me, and it shall be answered with a blessing upon their heads." (Doctrine and Covenants 25:12)
We don't use music that expresses our emotions as much as music that expresses our faith. True, they are connected, but while human emotion can be wild and unpredictable with many highs and lows, faith is solid and unmovable. This is what the Lord wants to see from us as we worship.
