In this site we need to mention Juliette Nadia Boulanger as she was the main reason for Astor Piazzolla to believe in his own music.
Nadia Boulanger was born in September 16th of 1887 and passed away in October 22nd of 1979. She was a French composer, conductor, and teacher who taught many of the leading composers and musicians of the 20th century, and also performed occasionally as a pianist and organist.
Coming from a musical family, she achieved early honours as a student at the Conservatoire de Paris but, since she didn't believing she had any particular talent as a composer, she gave up writing music and became a teacher. As such, she influenced many young composers, especially those from the United States and other English-speaking countries.
Besides Astor Piazzolla, among her students were those who also became leading composers, soloists, arrangers, and conductors, including Grażyna Bacewicz, Burt Bacharach, Daniel Barenboim, İdil Biret, Elliott Carter, Aaron Copland, John Eliot Gardiner, Philip Glass, Roy Harris, Quincy Jones, Dinu Lipatti, Igor Markevitch and Virgil Thomson.
Boulanger taught in the US and England, working with music academies including the Juilliard School, the Yehudi Menuhin School, the Longy School, the Royal College of Music and the Royal Academy of Music, but her principal base for most of her life was her family's flat in Paris, where she taught for most of the seven decades from the start of her career until her death at the age of 92.
Boulanger was the first woman to conduct many major orchestras in America and Europe, including the BBC Symphony, Boston Symphony, Hallé, New York Philharmonic and Philadelphia orchestras. She conducted several world premieres, including works by Copland and Stravinsky.