"Enthusiasm" is the notion that God can create saving faith in a person apart from God's Word and Sacraments (Holy Baptism and Holy Communion). It has a long history in modern Christianity, and has been discussed at great length over the centuries. (Check the wikipedia entry for more info.)
Or better, see how Historic Christianity views it. From the Formula of Concord, Epitome II, 6:
Likewise we reject and condemn the error of the Enthusiasts who imagine that God draws men to himself, enlightens them, justifies them, and saves them without means, without the hearing of God's Word and without the use of holy sacraments.
While this is no Theology blog, I do think it's important for musicians (and people interested in Music) to understand this. Without God's Word, saving faith cannot be conferred through experience or personal revelation.
How many times have we heard of someone being moved, in some deep spiritual way, through a work of art, a scenic vista, or a piece of Music?
Can Music really convey spiritual truths? Absolutely not (see above). Can it be conjoined with Scriptural texts to provide an edifying and artistic means of sharing God's Word? Absolutely. It is in this role that Music serves its highest purpose, as a vehicle for the all-powerful Words of God.
This truth explains why so many pieces of "old music" (including many tunes in the "old hymnals") are simply poetic versions of text taken straight from the Holy Bible.
Let's revisit our earlier question, with a twist:
If Music doesn't convey spiritual truth or saving faith, does it convey anything at all? And if so, what does it convey?
That is the question that forms the central core of what this blog is about. In fact, it is that very question that prompted me to begin a serious academic study of Music two decades ago. While it is difficult to synthesize, I think there is a way of answering that question that can be very useful to the musician, pastor, and layperson alike. Stay tuned!