The idea is like the seed corn; it grows imperceptibly in secret. When I have invented or discovered the beginning of a song …, I shut up the book and go for a walk or take up something else; I think no more of it for perhaps half a year. Nothing is lost, though. When I come back to it again, it has unconsciously taken a new shape, and is ready for me to begin working at it.

Johannes Brahms (1833-1897) German composer and pianist
Conversation with George Henschel
    (Source)

Quoted in a letter to Herr and Frau von Herzogenberg in Max Kalbeck, ed., the Brahms-Gesellschaft collection of correspondence, Vol. 2 [tr. Bryant (1909)], as cited in John Alexander Fuller-Maitland, Brahms, ch. 3 (1911).