NYON, Switzerland (Reuters) - Noted Brazilian musician Gilberto Gil, who says that struggle has been a counterpoint to his successful musical life, takes a road trip in the film "Viramundo" to seek out his musical origins in Brazil, Africa and Australia.

The documentary by Swiss filmmaker Pierre-Yves Borgeaud, which uses the lens of indigenous communities struggling to preserve their cultural identity after colonial rule, premiered on Saturday night at the "Visions du Reel", an international documentary festival in Nyon, Switzerland.

"Through musical encounters we were looking at the links between countries and their peoples who were submitted to domination and colonization, that was the case of Brazil, Australia and South Africa," Gil told a group of reporters prior to a sold-out screening at the festival.

In the film, producer Emmanuel Getaz accompanies Gil and his faithful percussionist, Gustavo Di Dalva, across the southern hemisphere, from Brazil's Bahia to Australia's Northern Territories and South Africa before returning to the Amazon.

It opens in Salvador where the slim Gil was born, 70 years ago. Dressed in the traditional and blue costume of the Filhos de Gandhi performers, he takes part in the pulsating Carnival.

He then flies to Sydney, where he meets Peter Garrett, Australia's education minister and a former lead singer in the rock band Midnight Oil. Gil reminisces about keeping up his music while serving as culture minister under former Brazilian president Luiz Lula da Silva from 2003-2008.

The next stop is a community centre in Redfern, an inner-city suburb of Sydney, where Aboriginal Patrick Dodson says, "There was never any recognition of our unique culture. The aim of Christianity and Westernisation was so that nothing remained of who we are as Aboriginal people."

Gil empathizes due to his experience, though he notes there has been some progress.

"In my country where black people were brought as slaves, they suffered and were humiliated and separated and whatever bad thing you can think of," Gil told Dodson. "Time passed and things changed. And now we can have a black minister."

The musical journey continues to Johannesburg, South Africa, where a young black trumpet player in the slum of Soweto is juxtaposed with a white woman violinist living in a gated house.

Both young musicians play in the racially mixed Miagi orchestra, but their personal stories take a backseat to a performance with Gil and South African activist and singer Vusi Mahlasela.

The two men perform a beautiful duet of "Tempo Rei", and Mahlasela then sings "Say Africa", explaining the Zulu concept of "ubuntu", which he translates as "a person is a person because of other persons."

The last leg of the odyssey is set in heavily indigenous city of Sao Gabriel da Cachoeira, Brazil. Here, a singer who describes herself as half Brazilian and half Indian sings the final, moving song about the degradation of the Amazon's fragile environment.

Gil sees his difficulties as a driving force in his life.

"Since my adolescence, I've been an activist in politics and the social struggle," he told the film's audience. "I got involved in the movement against the military dictatorship and was imprisoned for three months and expelled. Struggle is also an essential part of my story, an element of enthusiasm and an engine."

The film will open in France and Switzerland in early May, and expand in Europe as well as Brazil, South Africa, and the United States later this year.