I think most people would acknowledge there are some songs which are inappropriate for church worship. However, the real issue is where do we draw the line? To some, all “Christian songs” are appropriate for use in a church. To others, only a certain kind of music is allowed. How should we think through this issue?
Are there any passages which talk about this issue directly?
This is the first question to ask in working through any issue. Pertaining to this issue, Colossians 3:16 applies very appropriately (cf. Eph 5:19).
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.
Notice that the church is charged to teach and admonish one another WITH psalms, hymns, and spiritual songs. In other words, these are the means by which the teaching and admonishing take place. So, the important application needs to be that our church music and songs focus on correct doctrine. To put it in the negative, we are not to sing songs which are not accurate or true, nor helpful for the body of Christ.
Are there any biblical principles that we should apply to this issue?
There are a wide variety of scriptural principles that could be applied to this issue, but here are just a couple.
The God Test. Based on the first two commandments (Exod 20:3-4), I think it is highly appropriate to be reminded of the theological fact that God is not like anything else, and nothing else is to be treated like God. Thus, how we worship God should be unique from the way we refer to other things. In other words, if you could sing a song to your girlfriend AND to God then its probably not appropriate.
The Meditation Test. Philippians 4:8 is clear that only the true, noble, just, lovely, etc. ought to be meditated upon. Since singing is really just forced meditation, our songs (especially our worship songs in church), need to reflect a loveliness and appropriateness about them.
The Weaker Brother Test. I think based on passages like Romans 14, we can infer that we would never want to make another brother stumble with our music selection. Similarly, there may be music which at a lesser level simply annoys others in our church. If I have elderly saints worshipping in my congregation, I need to keep them in mind when thinking about music.
Are there any wisdom principles that we should apply to this issue?
Certainly God has gifted us with the ability to observe and use sound judgment on issues as well.
Singability. Some songs are just not written to be used in congregational singing. It may sound great on the radio, but it is just difficult to sing it in a united, cohesive way. Further, some songs may be too high in key, or too fast/slow in tempo. These considerations should be evaluated in wisdom.
Tainted Music. Some songs are tainted by association. For example, there is some modern Christian music which is written by heretics. If one were to use such songs, it might lead people to other (likely heretical) songs written by them. So, this is a tricky issue and should be seriously considered.
Repetition. This is a tricky subject too, because obviously there is repetition in the psalms. But, I think we need to be careful with repetition for the sake of repetition. The repetition in the psalms is not really that common, and it is always deliberate to draw our attention to something. Many of the repetitions in contemporary praise songs are simply to add filling.
Obviously there is much more that could be said on this important issue, but I think its a necessary start.