This is from a 1943 broadcast. Here is more on Toscanini and on the Grand Canyon Suite, which was written by Ferde Grofé.
The piece is divided into five sections: Sunrise, Painted Desert; On the Trail; Sunset and Cloudburst. The best known section probably is the passage in On the Trail in which Grofé uses the instruments to portray horses or donkeys traveling on the rocky surface. It starts at the 17:20 mark.
