Abraham Chasin performed the premier of his Second Piano Concerto with the Philharmonic Orchestra in March 1933. It was conducted by Leopold Stokowski:
At the first one [rehearsal], as I walked to the piano I was surprised to see Stokowski’s assistant, Artur Rodzinski, on the podium; Stokowski was sitting in solitary elegance in one of the gilded red-plush seats in the center of the hall. I had known that on the “first reading” of a complex score by an avant-garde composer, the orchestra was usually taken through its initial paces by Rodzinski. Evidently, my unexperimental, even romantic, score was also scheduled for a first reading – à la Schoenberg or Webern.
What I did not know until I was on stage was the existence of a complicated arrangements of green, red, yellow and blue lights on top of the conductor’s desk, which Stokowski manipulated from his seat to flash directions to Rodzinski to start, stop, play softer or louder, slower or faster. Rodzinski’s observable reaction to those bewildering gleams of light was sheer desperation. Afterward, he confided his resentment of this “traffic-light system”, calling it the most sadistic procedure he had ever endured.
That is how Rodzinski, the orchestra, and I rehearsed, and I rehearsed for a solid hour. At intermission, Stokowski came up to me and said, “I trust you understand that I rarely conduct the first rehearsal of a work new to me. I first listen so as to know what I want to do with the score – if I want to at all. I have definite ideas about your score. I don’t think you wanted everything that you put down. Do you mind if I change a few things here and there? And perhaps try out some things I think you wanted?” I said that I could only be grateful.
As the orchestra began to tune up, I returned to the piano. Then there was a sudden hush; the side curtains parted; and Stokowski, blue shirt open at the throat, flew in, sprinted to the dais, and in a high voice delivered some mumbo jumbo to the orchestra and sounded something like this “Chasins consharto firs’ mooment faw meshes after letter J – no, make it tree.” Down went the saberlike hands. I, the composer and soloist, was completely lost and had to scramble like mad to find the right place in time for my entrance, although the orchestra members came in precisely to a man.
It was not long before Stokowski called a halt. Completely immersed in the music, he called out with hardly a trace of an accent, “Second trombone, you be quiet here for eight measures. Third horn, I want you to play the first two measures and then nothing. All right. Letter P.” The second emerged with a totally unexpected clarity, and all I could do was smile my gratitude at Stokowski’s questioning face as he turned toward me. Later on, he stopped again and said, “That isn’t what you mean. I think it is this. Boys, you know that flutter-tongue effect? All right, let’s go.” There it was, just as I dreamt it, and so it continued right to the end of the work. Stokowski realized a dozen things for me that I had been unable to realize myself. A conductor like that is not by accident called an interpreter. He actually becomes a partner of the composer. This is one of the many reasons why Rachmaninoff regarded the Philadelphia as his favorite orchestra. He once remarked, “Stokowski has created a living thing. He knows what you want, he puts it in, and he infuses vitality into every phrase.”
Source: Chasins, Abram (1979) Leopold Stokowski: A Profile. London: Robert Hale, p.138-140.