Brendan King has sent me this excellent passage in which Beethoven reveals his passionate relationship with his Muse:
 
From “Composers on Music” by Josiah Fisk, page 56.

“I carry my thoughts about with me for a long time, often for a very long time, before writing them down. I can rely on my memory for this and can be sure that, once I have grasped a theme, I shall not forget it even years later. I change many things, discard others, and try again and again until I am satisfied; then, in my head, I begin to elaborate the work in its breadth, its narrowness, its height, its depth, and because I am aware of what I want to do, the underlying idea never deserts me. It rises, it grows, I hear and see the image in front of me from every angle, as if it had been cast like a sculpture, and only the labor of writing it down remains, a labor that need not take long, but varies according to the time at my disposal, since I very often work on several thinfs at the same time. Yet I can always be sure that I shall not confuse one with another. You may ask me where I obtain my ideas. I cannot answer this with any certainty; they come unbidden, spontaneously or unspontaneously. I may grasp them with my hands in the open air, while walking in the woods, in the stillness of night, at early morning. Stimulated by thse moods that poets turn into words, I turn my ideas into tones, which resound, roar, and rage until at last they stand before me in the form of notes.”