On today’s date in 1955, the Boston Symphony was celebrating its 75th anniversary season with the premiere performance of a brand-new symphony—the sixth—by the American composer Walter Piston. At the time, Piston was teaching at Harvard, and his association with the Boston Symphony went back decades. Even so, Piston paid the orchestra an extraordinary compliment, crediting its musicians as virtual partners in its composition:

“While writing my Sixth Symphony,” Piston wrote, “I came to realize that this was a rather special situation. I was writing for one designated orchestra, one that I had grown up with, and that I knew intimately. Each note set down sounded in the mind with extraordinary clarity, as though played immediately by those who were to perform the work. On several occasions it seemed as though the melodies were being written by the instruments themselves as I followed along. I refrained from playing even a single note of this symphony on the piano.”

This symphony may have been tailor-made for the Boston players, but Piston was practical enough to know other orchestras would be interested, and so added this important footnote: “The composer’s mental image of the sound of his written notes has to admit a certain flexibility.”