Composers and/or performers may intend a certain reaction to be experienced by listeners, and that reaction may occur, but this is neither essential nor universal in much music making, except in the very broadest sense that audiences (mostly) know when to applaud… in cultures that applaud.
Some of the intelligibility of music to typical listeners seems to be semiotic in nature, depending on very basic parameters like high/low, fast/slow, loud/soft, complex/simple, bright/mellow, etc. However, every generation experiences the fact that its “musical symbols” are different from the last, sometimes hugely so. In response to music that one generation finds teeth-grating, another generation closes its collective eyes in mellow nirvana. In other words, musical gestures and structures are not interpreted in a universal way, even among culturally related listeners.
It’s important not to confuse communication with expression and the perception of it. A listener can hear a crescendo, or a nice turn of phrase, and even respond to these on some level, perhaps by assuming a certain emotion on the part of the composer or performers, but the content of the communication is very difficult to define. This is not to say that music is not emotional in some absolute sense; it seems clear that sometimes composers and performers do feel things about the music, and sometimes audiences will feel some of the same things. However, the music and its performance may simply signal some form of emotional intensity, and the listener may easily infer a different emotion (as the one to be intensely felt) than the one “intended” by the composer or performer.
There are many theories of emotion. In order for a theory of communication in music to be based in its assumed emotional nature, it will be necessary to choose one of those theories first. Assumptions about the nature of emotion underlie most theories about the nature of musical communication. For a taste, try typing “theory of emotion” into a web-based search engine, and sample the variety of theories. Each one would have different implications for the nature of musical communication, if such a theory is based in the musical communication of emotion.
To illustrate the problem: everyone has a face, and uses facial expression to communicate, but the very same facial expression may express great pain or great pleasure. Tears may signal sadness or joy. A smile can be truly joyful, or darkly evil. In other words, communication via facial expression depends on a context understood by both parties to the communication, and is not inherent in the facial expression itself. There may be only a few distinct facial expressions, with all the subtleties inferred by the viewer of the expression. Emotions can be exceedingly complex, as any slightly introspective person knows. That does not mean, however, that the face actually communicates them with any great specificity.
Go here for an interesting experiment in facial expression. **NOTE: THE PREVIOUS LINK IS BROKEN. THE CONTENT THAT WAS THERE APPEARS TO HAVE BEEN MOVED. I AM TRYING TO LOCATE IT ELSEWHERE.**
How much more complex is musical structure and gesture than facial expression?
If musical symbols have been previously assigned (i.e., a melody stands for a certain person or place, etc.), some communication may be said to have happened, but it will be based on a simple sign or leitmotiv. Short of that, the communication may be said to be musical communication, about musical things… a tautology if ever there was one.
If music is primarily communication, and if the communicative potential is merely semiotic and very general, then the structural subtleties matter relatively little. That is, of course, the exact opposite of the professional opinion of virtually every music theorist, and not a particularly helpful point for the beginning of an attempt at faith-integration, particularly in music theory, because it invalidates the reason for most of the content, i.e., the study of the structural subtleties that matter so much to musicians.
If a theory of faith integration in music, and especially music theory, is to celebrate the inquiry into the subtleties of musical structure and gesture, that theory will need to be based on something more than the assumption that music communicates emotion, semotically or otherwise.