Stravinsky met Ravel in 1910 at the time of the first performance of The Firebird in Paris, and they remained close friends despite growing differences in their musical tastes and judgments. Their surviving letters to each other have an intimate and jocular tone which mark Stravinsky as one of the closest and most relaxed of Ravel's musical friends (Orenstein, : letters 97, 105, 108, 125, 223).
They were closest in the years before the First World War. In 1913 Ravel stayed with Stravinsky at Clarens in Switzerland and they worked closely together on a performing version of Moussorgsky's Khovanshchina (now apparently lost). According to Stravinsky, on an excursion to Varèse near Lake Maggiore they couldn't find separate hotel rooms, and so slept in the same bed (Stravinsky, , p.62). At the same time, Ravel was starting work on his Trois poèmes de Stéphane Mallarmé, for which he used a similar ensemble of instruments to Stravinsky's in the recently completed Three Japanese lyrics. The first song in Ravel's group of Mallarmé settings, Soupir, is dedicated to Stravinsky.
Their friendship was later ruffled by criticisms of each other's works. Stravinsky was present at the play-through of La valse for Diaghilev in 1920, but made no comment when Diaghilev rejected it ( Poulenc, ). Ravel disliked Stravinsky's opera Mavra and the ballet Apollo (1928) (Entretien, ). According to Poulenc, this coolness lasted until Ravel's death. However, Ravel's admiration for Les noces (1923) led to a warm if brief exchange of letters between them (Orenstein, , letters 223 and 224). And Stravinsky spoke fondly and appreciatively of Ravel after the latter's death (Stravinsky, , p.62-63).
Ravel had been one of the most ardent and perceptive admirers of The Rite of Spring on its first appearance, and Stravinsky recalled this in one of his lectures at Harvard University: "I hold that it was wrong to have considered me a revolutionary. When the Rite appeared, many opinions were advanced concerning it. In the tumult of contradictory opinions, my friend Maurice Ravel intervened practically alone set matters right. He was able to see, and he said, that the novelty of the Rite consisted, not in the 'writing', not in the orchestration, not in the technical apparatus of the work, but in the musical entity." (Stravinsky, , p.9-10).