Among the innovations of sound editor Alan Splet, who won a special Oscar® for his work, was attaching microphones to the underside of the horse during the racing scenes to catch his actual hoof-beats and breathing.
The Black was portrayed by a champion Arabian stallion from Texas named Cass-Ole; his friend, the old white horse named Napoleon, was portrayed by Junior - who had previously appeared in National Lampoon's National Lampoon's Animal House (1978) as Trooper, Neidermeyer's horse.
After the scene of the ship sinking, there is a stretch of 28 minutes where no dialogue was spoken.
Cass Ole, like most horses, had his mane trimmed into what's called a bridle path. This makes it easier to fit a bridle. For the movie, Cass Ole had to wear "hair extensions" to make his mane look like a wild horse's mane. He also had white markings on his legs and forehead and the white needed to be covered with a black hair dye to transform Cass Ole into the Black Stallion.
Author Walter Farley had reservations about his signature story being filmed and feared that the novel might not translate successfully to a new medium. Happily, the movie exceeded his expectations in remaining true to the original and finding its own artistic identity. "They did a beautiful job," he conceded.