Harmony in Blue: The Duet may date from the winter of 1877 to 1878, but is not completely consistent with Whistler's usual technique and style of painting. 1

1877: According to John Hollingshead (1827-1904), Whistler attended the last rehearsals at the Gaiety Theatre of the Grasshopper, Hollingshead's adaptation of Meilhac & Halévy's La Cigale, in which a caricature of Whistler painted by Carlo Pellegrini (1839-1889) appeared. 2 It opened on 13 October 1877.

A rough wash figure composition, known as Theatrical sketch [M.0672], is to some extent similar in subject and technique, and may be related to the oil. It is therefore assumed to date from the same period, but does not actually help to date the oil.

1877-1878: At the Gaiety Whistler made numerous pen drawings of the accompanying burlesque, Little Dr Faust, by H. J. Byron, including r.: Masked girl wearing a head-dress skipping; v.: Dancer [M.0663], r.: Nellie Farren; v.: Demon [M.0665], r.: Demon; v.: Two sketches of Nellie Farren [M.0666], r.: Two sketches of Nellie Farren; v.: Studies of two actors or actresses, one playing a banjo [M.0667], r.: Demon; v.: Young woman [M.0668].

He also made sketches of other theatrical scenes, including Venetian Carnival [M.0669], r.: A man serenading a woman in a balcony; v.: Lovers embracing [M.0670], Carnival at Venice [M.0671].

1878: Whistler wrote to Walter Theodore Watts-Dunton (1832-1914) on 12 January 1878 that he wished he could paint the star of the show, Ellen ('Nellie') Farren (1848-1904). 3

On 20 January 1878 Alan Summerly Cole (1846-1934) wrote in his diary that Whistler was 'Whistler painting scenes from little Dr. Faust at Gaiety which may turn out well.' 4 These may have been related to Harmony in Blue: The Duet.

A pastel study of three theatrical figures, Souvenir of the Gaiety [M.0664], may also be related to the studies and drawings mentioned above, and has also been tentatively dated 1878.