Catalog of Birds: "'Then comes a further difficulty, the reproduction of timbres. If I want to reproduce on piano, let's say, the song of a garden warbler or a nightingale, I need to find a complex of pitches for every melody-note. Each note of the melody is furnished with a chord. It consists quite simply of conforming to reality, not only to the birdsongs, but also to everything surrounding them: the landscapes, fragrances, colors, and above all, the passing of the hours during the day and night. It's very complicated. "