In order to emphasize the abstract nature of his paintings, whistler often chose titles that were more commonly used in

The missing word and the answer is music.

James Abbott Mcneill Whistler was a leading proponent of the credo "art for art's sake". HIs revolutionary methods changed existing approaches to pastel, oil paint, etching, watercolor, and also interior design. Finding a parallel between painting and music, he entitled many of his works "harmonies", "nocturnes", and "harmonies" that emphasizes primacy of tonal harmony. 

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