in my head

The intensity and thoroughness of his formal training, coupled with years of self-schooling, enabled him to separate the process of painting into stages: a generative, conceptual phase and an executive, process-oriented one. In the first he conceived the complete work almost in its entirety, much as an experienced chess player plans a number of strategies before making a move. In the second he would paint an entire canvas quickly, so that it retained the freshness of a wonderful accident. When asked, “How can you paint a big picture so quickly?” he replied, “because I’ve already painted it in my head…Just putting it on the canvas, that’s nothing."

“Milton Avery: The Late Paintings” by Robert Hobbs, Milton Avery: The Late Paintings (Harry N. Abrams, 2001).