This might contradict some of the intentions and perhaps assumptions behind some of the posts in this thread, but here it goes. In some of my posts recently I've been quoting from Collingwood's
Principles of Art (see
this post on the positive dissociation thread, for example). Without getting into all the details, Collingwood distinguishes art (the expression of emotion) from magic (the production of emotion for use in practical life). (I think his ideas of 'magic' might be in line with some of Gurdjieff's writing on 'objective art'. But that's not where I want to go here.)
If there is an esoteric 'meaning' to certain traditional forms of music, it might be helpful to think of them in 'magical' terms, the way Collingwood uses the term. Especially when combined with myth and ritual, in the context of an entire 'religious' worldview, music will serve a practical purpose in evoking the emotions necessary to continue the way of life of the people who produce such music. I don't think there's necessarily anything special about the music itself (e.g. any kind of special 'esoteric' properties), but rather that
its place within the wider sphere of 'magical' practice produces the emotions, the sense of community through shared emotion, and the inspiration for certain practices (whether trance-inducement, a warlike mindset, patriotism, etc.)
But what about the music itself? Reading Collingwood's book reminded me of a book I read several years ago and which is one of my favourites: Deryck Cooke's
The Language of Music. From the book description:
First published in 1959, this original study argues that the main characteristic of music is that it expresses and evokes emotion, and that all composers whose music has a tonal basis have used the same, or closely similar, melodic phrases, harmonies, and rhythms to affect the listener in the same ways. He supports this view with hundreds of musical examples, ranging from plainsong to Stravinsky, and contends that music is a language in the specific sense that we can identify idioms and draw up a list of meanings. The book's final section analyzes two symphonies, Mozart's Fortieth and Vaughan Williams's Sixth, to explore the nature of musical inspiration and the process whereby the notes actually convey emotion from composer to listener.
I'm not sure if Cooke read Collingwood, but their ideas are very similar. In the description above we can see how music can be both 'art' and 'magic'. As art, it will express emotions, but as magic, it will be purposely written to evoke certain emotions (usually in a cliched sense, as in pop songs, dance tunes, and potboiler film scores, as well as ritual music, the liturgy, national anthems, military songs, etc).
Cooke argues that at least in the Western tradition (he doesn't go so far as to say the 'meanings' he finds are universal, only that they are universally adhered to by Western composers) that certain melodic fragments and intervals evoke similar emotions. E.g., the minor sixth falling to the dominant fifth is the height of despair and sadness (e.g. F to E in A minor).
I'd just add that I don't think he's entirely correct. The falling minor sixth is not
equivalent to despair. If it were, it would simply
be despair. There would be no need for the music. Rather, it evokes a feeling like despair. It is the musical expression of despair, and hearing it is heart-wrenching in a way that actual despair isn't, simply because it is a musical experience and not any other. As Collingwood put it, "the emotions which we express in music can never be expressed in speech, and vice versa. Music is one order of languages and speech is another".
So if music is esoteric, I think it is esoteric in the sense that, to us,
emotions are largely esoteric. Our emotional centers need work. We block certain emotions from consciousness, thereby corrupting it. And that will affect our listening to certain pieces of music, e.g., those that evoke certain uncomfortable emotions, or emotions which are perhaps too 'high' for us to resonate with. Perhaps we may not even be able to connect with certain types of music (e.g., from certain other cultures), because we are not ingrained in the full way of life in which such music serves its purpose. It expresses and evokes emotions with which we're unfamiliar and which serve no practical purpose in our daily life. But at the same time, certain forms of music may
help in evoking emotions within us that we have yet to get in touch with. In that sense, along with the composer, we can 'express' an emotion which beforehand we had not brought to consciousness. And with it thus expressed, we have
learned something and our emotional palette has become a bit more refined. And that emotional refinement will carry over into other areas of life: we will be more perceptive to the emotions of the moment.
So, in conclusion, maybe music is esoteric after all, but in the sense of the role it can play in self-knowledge and the expression of the depths of human feeling.