Robert de Fragny recalled a conversation with Ravel about his compositional process:

The G major Concerto took two years of work, you know.  The opening theme came to me on a train between Oxford and London. But the initial idea is nothing.  The work of chiseling then begun.  We’ve gone past the days when the composer was thought of as being struck by inspiration, feverishly scribbling down his thoughts on a scrap of paper.  Writing music is seventy-five per cent an intellectual activity.  This effort is often more pleasant for me than having a rest.

Echo Liberté, 7 November 1950. Cited in:  Nichols, Roger (1987) Ravel Remembered.  London: Faber & Faber., p. 61.