The Carmelite Order has had a presence in Brazil since before 1759. This stamp (Scott 893) commemorates the bicentennial of that presence in 1959. It was issued on July 16 of that year. This site gives some information on the churches in Rio de Janiero, but no details relevant to organs in any of them.
Update (7/15/11): With the help of another blogger I have found this site which is a dissertation on the organ, located in a monestary. The dissertation is quite complete, dealing with various construction details. Sadly it's in Portuguese, however the synopsis is in English.