Coleridge, for example, who described writing the lines
In Xanadu did Kubla Khan
A stately pleasure dome decree:
while in an opium-induced state and then, interrupted by someone and distracted, left the writing-table to come back to it. As indeed he did, for he eventually came up with:
In Xanadu did Kubla Khan
A stately pleasure dome decree:
Where Alph, the sacred river ran
Through caverns measureless to man
Down to a sunless sea.
And much more; but there is a time and space constraint here which does not permit the full poem. Look it up and read it sometime, I'm certain you'll find it enjoyable.
The point being that he started the poem under head and probably came back to finish it when he was level. The idea came in an alternate reality and when we come down to it the idea is the key to creativity and the rest is just the execution of the idea, the bringing of it to fruition: seeing it on canvas or paper or word processor, or listening to it on MP3, or dancing out a special dance.
There are many forms of Art and many ways of expression. The classically trained musician works to replicate the music of the creative geniuses. Practice and more practice each and every day. He feels the music, he can replicate the music but he cannot or will not create it. So, is what he does Art? I suspect that it is talent, yes, but I guess not Art, for the role of the Artist is to create and while the one who replicates does in that act create, the creation is another's. He merely mirrors it. Many can imitate Picasso, yet who among them can create his themes? Where do the ideas, verses and melodies of the songwriter come from? Does he sometimes lower his bucket down into the subconscious by whatever means to conceive and create his Art?
Art varies and there are many forms, some much more difficult than others. Art does not depend upon who the artist is. It only depends on what the artist creates. It cannot exist without it's creator. Art is Art, full stop. You know it when you get it. You feel it somewhere deep inside of you.
What fuels Art? Is it genetics? Or is it what is absorbed in the womb? Can Art be taught?
More to the subject point is the question: what is the real relationship between the creation of Art and the influence of depressants and intoxicants upon the mind in the process of that creation? Does substance abuse influence Art?
On the other hand, does a person who exercises regularly have a better grip on his or her Art than someone who does not? Does exercise give birth to artistic inspiration? And if not what does?
Many questions, few answers. This remains a difficult and controversial subject.
Still, much of what we consider to be Art comes to the creator through the subconscious mind, and often the channel between the conscious and the subconscious entails twisting the mind sideways.