I've recently been thinking about Colossians 3:16: "Let the word of Christ richly dwell within you with all wisdom, teaching and admonishing one another with psalms and hymns and spiritual songs, singing with thankfulness in your hearts to God."
We usually use this passage as justification for singing. However, that's usually as far as we take it. I want to point out what Paul said in the middle of the verse: "teaching and admonishing one another with psalms and hymns and spiritual songs." Notice the emphasis of Paul's instruction. He defines the music by its content, not its style. He didn't say, "chants and rounds and four-part harmony," or something else to identify the style of music we sing.
There are two points we can draw from this detail. First, we are, I believe, at liberty to use whatever style of music we desire in our worship, so long as it consists strictly of singing.
That said, the second point is a caveat to the first. Our emphasis is to be on the words we sing--not the music. While I, and other song leaders, may get up and do my best to make sure that a congregation sings correctly from a musical perspective (keeping time, in key, etc.), the words are the vehicle through which we "teach and admonish one another." Because the emphasis is on the words, the music should not overshadow the words. While I am not, as a rule, opposed to songs written during the past 15-20 years, the majority of the songs written in that period (I have no reliable statistic, just a feeling from what is popular among that music) leave me feeling as if the words are a justification for singing a particular tune. That is, the goal is to achieve an effect, rather than to edify.
For example, the song "The Greatest Commands." The song is essentially verbatim from the Bible (1 John 4:7-8; 1 Corinthians 13:7; Matthew 22:37). However, all four parts sing different sets of words (alto sings from 1 John; bass sings from 1 Corinthians; tenor repeatedly sings "God is love;" soprano sings from Matthew). One can only catch snippets of what is being sung and is left with little more than a general feeling of the music. Yes, it's a beautiful song. Yes, it's Scriptural. The question is, is the main attraction the words or the music?
There are other songs that have everyone singing essentially the same words, but incorporate some pretty showy musical effects (I call such songs the creations of music-theory madmen). Again, are we singing because of the words, or because we like the way they sound?
I'm not criticizing anyone for liking songs because of the music. There are a few songs in our hymnals that I like because of the music. I think, however, that we need to be careful not to spend more time appreciating the music than we do appreciating the words.
Incidentally, I should add that nearly all the songs with which I have this particular problem were written by members of institutional churches. I say this because the liberal churches (especially the mega-churches) have begun to move toward instrumental music. While most still adamantly oppose it, there are a couple of congregations that have incorporated instrumental music in some of their worship services. These songs, I believe, contribute to that decision. They have, essentially, replicated some of the musical features of instrumental music in a more acceptable form. It was only a matter of time before the dominance of these songs, in addition to the use of praise teams and such, led those congregations down that path. Let's be careful not to follow them!