Martinů's one substantial essay from his Notebook from Darien (1943), “On the Creative Process,” features his account of the “initial impulse” at the inception of a musical work and how the composer responds. One of his goals is to refute the idea that the composer transmits meaning concretely, or that the listener can retrace the composer's emotional world in the music. At the opening of his essay, he describes the state by which the composer realizes the initial impulse as “subconscious concentration,” a premise having wide-ranging implications on his thought.

Although his idea of subconscious concentration is based on his own practice as a composer, he provides only a few examples of how this came into play in his works. Thus to shed light on this idea, we can take note of two experiences from his youth that he relates to Šafránek in a letter from 7 June 1958, which comes from a time the two men were corresponding at length over drafts of the second biography. Employing the term “open mind” to describe a certain state of freedom from conscious thought, Martinů clarifies the import of what he had once observed from taking part in a dictation exercise at the Prague Conservatory:

He then revises another account by Šafránek about how he had suddenly found himself working in a similar state. In this case, it was while producing the sketch to what he considered to be a conceptually complete work.