Unlike some conductors, Stokowski was known for playing the orchestra as though it were one big instrument at his command. According to his mood at the moment, he changed the tempo, he repeated passages that had never been played a second time in rehearsal, he muted the violins and gave the melody to the woodwinds. The musicians couldn't take their eyes off him.
Stokowski also responded to the mood of his audience, in particular, the group who comprised the Youth Concerts in the 1920s.
I was one of those in the 15 to 25 age group (IDs required) who adored him. Each month he provided some sort of surprise; I remember hearing Kirsten Flagstad once, and Laurence Tibbett at another time, unannounced in newspapers or the evening's printed program. At one of the early concerts he introduced Ravel's "Bolero'' as an encore, and the crowd went wild.
"Bolero'' in a recording, or used to accompany a ballet, I find boring. The same sequence of notes is repeated over and over and over again. But when played by a live orchestra, it begins with a scarcely audible whisper of sound (a brush moved across the top of a drum?). Then it is joined by a thin blue thread of melody. One instrument after another sneaks in, with each addition subtly changing the texture of the sound and adding to its volume. It builds to a crashing climax, impossible to reproduce in recorded form.
In the Academy of Music, with a student audience, "Bolero'' was wonderful, and the young people couldn't get enough of it. At the next concert, when Stokowski bowed his way out, the audience sat down, and so did the orchestra. Stokowski reappeared with the score for the planned encore, and the audience reacted politely - but refused to budge. "Bolero''! was the cry. Finally the conductor reappeared, took the podium, and "Bolero'' it was. And so it remained as long as I attended those concerts: The audience refused to go home until they had heard their favorite number.