One of the changes I have noticed in worship services during my memory (about 20 years) is that we seem to sing fewer and fewer traditional hymns and more and more "praise songs." I have nothing against praise songs, in fact I love singing them, but I fear the pendulum has swung too far.
One of the things that concerns me is that most praise songs don't accomplish the things we were told to do when we sing:
Col 3:16 (ESV) Let the word of Christ dwell in you richly, teaching and admonishing one another in all wisdom, singing psalms and hymns and spiritual songs, with thankfulness in your hearts to God.
It seems clear to me from this passage that Paul is saying that one of the things we are supposed to do while singing is teach. To do this, at least some of the songs we sing need to convey deep spiritual truths; they should express the things we are to do, the thoughts we should think, and the emotions we should feel. Our songs should lift not just our hearts, but our minds.
Now don't get me wrong, I'm not saying we shouldn't sing songs of praise. In fact, we are also commanded to sing songs of praise. What I am saying is that a lot of newer "praise songs" express great joy, praise, and fellowship, but don't convey theological truths. As a consequence, the less we sing the more traditional hymns, the less we actually teach as we sing.
Just food for thought.