Hi, tony: Forgive me for being brief; I'm having trouble transferring material over here right now.
But, yes -- to make a quick grab -- your own Catherine Benamou, Simon Callow in several chapters from Hello Americans devoted to IT'S ALL TRUE, and Michael Denning in his book, The Cultural Front: The Laboring of American Culture in the Twentieth Century, all make the point that Robert "Bob" Meltzer was involved in a collaborative effort with Welles and others to develop a scenario and script for IT'S ALL TRUE.
Because of his association with the progressive populist Chaplin, his friendship with Welles, and his background as jazz pianist in modern musical forms, Meltzer was early on given the task of establishing parallel story lines between the evolution of American Jazz, Mexican Mariachi/ Folklorico with the Samba and other South American dance movments.
In Rio, Meltzer seems to have taken on the tasks of factotum formerly the duty of John Houseman, Paul Stewart, and of course, Richard Wilson. Not only did he handle a lot of the Mercury Unit's PR, but he was put in charge of a group of scholars and journalists to produce a series of cultural studies concerning Brazillian folk dances and music. These led to the creation of the central Brazillian figures of the "Carnival" section, and as close to a conventional scenario and shooting script as IT'S ALL TRUE ever had.
Benamou, as you will know, makes this "auteural collaboration" a main thesis in her book. Callow gives evidence that, according to the enraged RKO Company Men, Lynn Shores and Tom Petty, Welles repeatedly left Meltzer in charge of shooting large portions of IT'S ALL TRUE, particularly those involving black residents of the favelas, which prompted repeated efforts to have him removed from the picture. And Denning discusses in some detail the parallels with American Jazz History, especially in connection to the art of Louis Armstrong, Duke Ellington, and Mead Lux Lewis.
Shores and Petty thought, after a falling out between Welles and Meltzer, that they could turn the latter into a dedicated Company agent, but upon Welles' return from South America, Meltzer -- by then a producer in Radio -- gave him the Ceiling Unlimited series, with scripts by Arthur Miller and others.
As you know, we have been over some of this ground back in 2006:
http://www.wellesnet.com/phpbb/viewtopi ... sc&start=0
And for what it's worth, though I do not take up Meltzer, whom I had just discovered, here is my review of Hello Americans, which has some further detail on the history of IT'S ALL TRUE: