If you can understand Charlie Brown's teacher, you can understand that music communicates, but first, let's take a look at how understandable words are, by themselves.
Have you ever noticed that missunderstandings are easily started through textual communication? With the advent of email, many businesses have found it necessary to advise their staff to be careful what they write in emails for precisely this reason. This same tendency can also be observed in social networking and online forums. In a text driven environment, meaning can be lost or even reversed, in some cases, in the mind of the reader, simply due to a lack of “tonal” information. Since, tone of voice, and even facial expressions, contribute significantly to effective communication, care should be exercised in seeking to understand a textual communication in their absence.
So in spoken language, we can readily acknowledge that how something is said is often just as important as the verbal content of what is said. For example, I can say the words, “I love you,” and alter my tone of voice to communicate meaning that is sarcastic, deep, flippant, casual, questioning, or even completely opposite of what the words would seem to say. Context also plays a role in this, since the words spoken in my home, alone with my wife, will likely carry a different connotation than if they were spoken in church to the whole congregation.
Moving beyond the text, it is possible to communicate (more generally) with only the tone of my voice. Remember Charlie Brown's teacher? Isn't it interesting that you could understand, "Whaah Whaah wa wa Whaah Whaaaaahh?" The cues from the other characters and the context provided enough information that your imagination supplied words that went perfectly with the rising and falling of her voice. Then there was Woodstock and snoopy…no words, but you could clearly understand what was being “said” simply with tones and visual context.
To suggest that these characters don’t communicate would be silly, but we should observe that they don’t have the precision of communication that would be added with the inclusion of words. The fact is that music is just like tone of voice, it can and does communicate, though its communication is fairly general. It is as if music simply amplifies the tone of voice. So to suggest, as some Christians like to do, that music does not communicate apart from the words would be just as incomprehensible as suggesting that tone of voice does not communicate apart from the words. You can do, with music, everything that you can do with your tone of voice…often better.
Some would like to run with this idea and begin to construct a taxonomy to describe the communication of music in precise terms, but this is the equivalent of trying to build a taxonomy of tonality in language. Such an effort is doomed to fail, because while tone and music do communicate, they are (at best) general approximations of meaning. There is absolutely no precision to it, and the situational and cultural contexts both play a critical role in understanding the expression.
In any case, it really doesn’t matter how it communicates; the fact is that it does. When we can observe that it is even possible to musically mock good doctrine with exactly the same words you use for proclaiming it, we should be driven to consider carefully what our music is communicating to the audience. As pertaining to how we approach worship music, we must understand that music is a crucial part of the over-all message, and how we sing matters as much as what we sing.