[EDNOTE.  [Carolyn Kunin sent in her announcement of the correct answer at almost the same time that Anthony Stadlen, unbeknownst to her, submitted that answer to the List.  -- SES] The correct answer is Diaghilev was responsible for all those ballet scores composed by Stravinsky, because he commissioned them.
 
Jansy Mello: Now that I got the answer (CK's and Stadlen's) I could google-focus on Diaghilev.  He is a distant cousin of the Nabokovs!
Here are more speficic informations and other links to Stravinskii, Diaghilev and the Nabokovs:
 
Thirty years ago, the composer Nicholas Nabokov, a distant cousin of Diaghilev, told me that there were, for Diaghilev, three kinds of composers: the kids, young men that he could dominate; the grownups, like Debussy, whom he could not; and, in a category all to himself, Stravinsky. ...Diaghilev's relationship with Stravinsky, the most, productive and important of his life, stretched over 20 years from the commission for Firebird in 1909 to their last collaboration, Apollo in 1928. Indeed, Stravinsky was crucial in the artistic development of the Ballets Russes, his works rarely out of the company's repertoire. Hardly a month went by without contact with Diaghilev, to discuss ideas or work in progress, yet the friendship between the two men was always uncomfortable. In his books of conversations with Robert Craft, published between 1958 and 1969, Stravinsky rarely has a good word to say for Diaghilev, although he was much more generous during a long discussion I had with him in 1966....
It was Stravinsky who introduced Diaghilev to Manuel de Falla in 1912. Nabokov put Falla among the composers to whom Diaghilev was not close and whom therefore he could not influence. ...Massine recalled to me how much emphasis Diaghilev, who dictated the work's dramatic shape,placed on a brilliant finale, but the piece is much more than a Fantasy on Spanish Themes, and remains one of Diaghilev's greatest commissions, proof of his extraordinary ability to draw the best from composers, even in unpropitious circumstances. nearly 70 years later, we see that not only Stravinsky and Falla, but composers as different as Poulenc and Prokofiev did their best work for him. Where are the Diaghilevs of today? Dancing with Diaghilev - ChesterNovello www.chesternovello.com/Default.aspx?...
 
Diaghilev: A Life - Resultado da Pesquisa de livros do Google books.google.com.br/books?isbn=184765245X...Sjeng Scheijen - 2010 - Biography & Autobiography VLADIMIR NABOKOV AND THE WORLD OF ARTwww.units.muohio.edu/.../shapiro.pdf -
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