If I remember correctly, I believe Paul Misraki actually wrote some music for the Carnivale section of the film, including the Urca Casino finale. This music is in the Lilly Library's Welles archive. But if Welles could have gotten Villa-Lobos to do FOUR MEN ON A RAFT, that would have been a real coup. Here's an excerpt from a brief essay that Welles wrote on Villa-Lobos at the time that suggests he may have been trying to woo him in some way for the film:
'New note in music: Heitor Villa-Lobos, Brazil's greatest composer and quite possibly South America's as well, made his debut in this country last Nov. 26th, appearing as guest conductor with the Janson Symphony Orchestra at LA Phil. auditorium. Villa-Lobos stirred his American audience into a new sense of art music. For the most part up to now, the radio and phonograph and dance orchestras of musical shows have kept us supplied with a steady flow of Latin American music. But with Villa-Lobos, Americans gained a new conception of South American musical culture. With unusual, powerful imagery, Villa-Lobos combines the rediculous with the pathetic. He is the Rabelais of the new music.
'With a laughter that is generous, rude and gusty, his is an art at once impetuous and vehement, sensuous and sentimental, copious and effusive. Of himself, he says, "I have always been, and remain, completely independent. I claim to be all myself in complete independence and isolation. Better bad of mine then good of others".
The first time Villa-Lobos's reputation extended outside the boundaries of South America was when he went to Paris in 1923. His success was instantaneous.'
BTW, for anyone interested in Carlos Chavez's music, this excellent 2-CD set of the 6 symphonies is available for fairly cheap. I have it, and I think it's great.