Here's another interesting passage...
1 Corinthians 14:15 What am I to do? I will pray with my spirit, but I will pray with my mind also; I will sing praise with my spirit, but I will sing with my mind also.
Paul is urging the Corinthians when they speak to speak in a way that "speaks to people for their upbuilding and encouragement and consolation."
I think sometimes we "sing to ourselves" in worship. We sing songs that make us happy, but don't necessarily edify the body. It's difficult sometimes to find the balance. I love new songs, but it's pretty obvious that not everyone likes the music I like. I need to be mindful to sing in a way that will communicate and edify, not just to make me feel good.