I have not seen the show yet, but bought the beautifully produced catalogue at the Met. All the essays examine the show's focus: Matisse's work in pairs, trios or series. Landscapes, still life, interiors, nudes--these genres at the heart of Matisse's painting--saw intense experimentation in the re-working of an original. What is striking about Matisse's pairs is that they were very often painted in the same format and size. These were very controlled experiments. More radically, they were also shown by Matisse as finished paintings in their own right. The sketch was traditionally hidden from sight but not Matisse's. Later in his career, he showed, together with the painting, the photographs that documented the progress of the painting. He was responding to the charge of easy conservatism. He insisted that he was a painstaking artist who was constantly pushing the boundaries of his art.
Of Interior in Yellow and Blue (1946) and Interior in Venetian Red (1946), Matisse wrote to an old friend, quoted in the essay by Cecile Debray:
Wishing to make a kind of painting that is related to my drawings, those that come to me directly from the heart and are traced with the greatest simplicity, I have set out on a very hard road that seems troublesome to me because of the little time that my age will grant to me. And yet, to be at peace with myself, I cannot do otherwise. With the sort of color relations that I am led to use to render what I feel, freed from the accidental, I find myself representing the objects without the vanishing lines. I mean FRONT VIEWS, one almost next to the other, linked to one another by my feeling, in an atmosphere created by the magical relations of color. To be logical why not use only local tones, without reflections? Human figures on the same plane as in a game of Aunt Sally[;] on these elements of simplified representation, put a color coming from the exalted local tone, or even invented altogether in accordance with my feeling, warmed by the presence of nature itself--a kind of poem.