As philosopher Martin Heidegger points out in one of his many lecture courses, there is something so immediate and easy about applying the word 'expression' to artistic accomplishments and activities and yet it could be argued to be a hollow descriptor.
Indeed, expression could be said not just of art, but of someone cursing, of a dog barking, of a child laughing, of a politician talking and so on. It doesn't really capture something essential and specific to artistic creation.
Of course I'm the first to admit that it is a handy word that captures a basic idea of pressing something outward from within and I suppose artistic creation does involve an element of that.
However if I were to choose a word that captured the intent and venture of artistic doings it would be the word statement, understood not just politically or verbally, but as a usually autocratic assertion of a quantum of energy and life force that occasionally transcends the destructive element of the creative deed.
Be it a piece of music, of architecture, a movie, a piece of visual art, a comic strip, a poem, a piece of literature, even a video game, all communicate a ready formed état de faits, that is, a statement occurring within the world that can take on a life outside and beyond the creator's inner life at the moment of inception and completion.
I would argue further that the more successful an artistic creation, the more it transcends the individual creator and reaches the imagination and sensibility of the spectator or listener, giving him a moment of self-release, of losing him or herself in the (hopefully) open-ended statement that has been made by the artist, perhaps in a fleeting perception that all things are connected and our lives, however disparate, are interlocked and intertwined as members of the human species.
Artistic expression or, as I prefer, artistic statement would thus contain in the best of cases an element of expanding consciousness, which is none other than the force of love as opposed to fear (which in opposition to love is the force that shuts consciousness down).
Great artists could therefore be argued to be light workers in the sense of bringing illumination to the darkened minds of individuals trapped in conventional ways of thinking. It was indeed Heidegger who defined art's task as setting truth to work, truth being understood widely as that which is, Being itself.
To be sure, not all art is light work expanding consciousness and sometimes art can be used to darken minds and contribute to the obscurantism, i.e. the general state of unenlightenment, of the world. Thus, artistic statement can be employed both to reveal or to conceal; in the first case the statement smacks of magic which influences change to occur with higher will (natural law) and in the second of sorcery which influences change to occur with selfish will (ego).
As students of the occult will know, symbolic knowledge can be used for good in the sense of expanding people's consciousness in which case it is light occultism or, on the other hand, can be used to manipulate and control others in which case it is dark occultism.
This is all very Star Wars I'll admit but the dark and light sides of the force exist here on earth for those who have understood the allegory of those movies allegedly set in a galaxy far, far away. Art does not escape this duality in nature and can partake of one or the other or even both sides of the force depending on whether it springs from the polarity of love or the polarity of fear.
So, to conclude, even though art may initially be a form of expression for creators, it is ultimately the statement it represents in the world that determines its position regarding the love-fear polarity, the light or the dark side of the force, the illumination or the darkening of men's minds.