The Sonata for clarinet in B flat and piano was sketched in 1959 and finished in 1962. It was first heard on 10th April 1963 in New York and was published in 1962 by Chester, with a dedication 'to the memory of Arthur Honegger'.

From Rocamadour, which he had discovered in 1936 and where he had returned to the Catholic faith, which was to remain with him, Poulenc confided to Simone Girard in 1959, 'I’m working. I’m finishing the lament of a Sonata for clarinet and piano dedicated to Arthur's memory. I think it's quite moving.' Aware that for him 'concentrating on woodwind is the solution ... at the moment' and 'simmering in the same pan, the Sonata for oboe and the clarinet one, ' Poulenc indeed wrote a clarinet piece which mirrors the other. As Renaud Machart points out, the three movements of the Sonata for clarinet follow an inverted plan with a sober Allegro tristemente including a très calme central section, a Romanza and an Allegro con fuoco. Their surface melancholy and poetic syntax are nevertheless similar. The tenderly sad atmosphere of the très calme and the Romanza (the former lament) evokes to some extent the most intimate pages of another late work for voice and piano, La courte paille, reminding us that from the same creative personality and from the same inspiration there had sprung compositions sometimes serious, sometimes joking. 'When people know all my choral works - sacred and profane - better, they'll have a better idea of my personality and see that I am not merely the light composer... of Les biches, ' added Poulenc vehemently. He dedicated one of his last works to Arthur Honegger, the first of Les Six to die. Though they had known each other a long time, they were only really close during Honegger's last two years, when he was ill. 'Arthur found [ my music ] too light and... I found his too heavy! ... We respected each other a lot, but we didn't like each other's music till towards the end of Arthur's life.' (Poulenc, Moi et mes amis). The Sonata for clarinet and piano was performed three months after Poulenc's death, on 10th April 1963 in New York's Carnegie Hall, by Benny Goodman and Leonard Bernstein.