Composed in September 1959, this is Poulenc's last work for two pianos. It is dedicated to the memory of Princess Marie-Blanche de Polignac, a long-time friend and patron of the composer, who passed away on February 14, 1958. Although the exact date of its premiere is unknown, Poulenc stated in letters to close friends that he was preparing this work for two American pianists he called "Les Boys," Arthur Gold and Robert Fizdale. Therefore, it is highly probable that the premiere was given by these two.

The work is accompanied by Poulenc's comments, which offer performance instructions:

• "Play as if improvising, with a cigarette in your mouth and a glass of cognac on the piano."
• "All syncopations (like the echo of the preceding chord) should be touched very lightly."
• "Overall, do not mute the pedal too much."

Furthermore, as indicated by its subtitle, "of alternating chords," this work, fundamentally composed of a succession of chords, is ingeniously structured so that the same piano does not play identical phrases. Even in passages where one piano seems to play a single phrase, the phrase is actually divided between the two pianos, ensuring both are treated equally. Though a work of approximately five minutes, it is a piece that crystallizes Poulenc's experience as both a pianist and an accompanist.