'Some of the performers have mental health issues. Some have been surviving on the streets of Rio de Janeiro for weeks, many of them for years. They live on Brazil's margins, but together, they sing as the choir With One Voice, a music project that aims to bring Rio's unseen people - "o invisivel" - to popular landmarks, giving them a stage from which to be seen and heard through song. 

'"The spotlights of the world are on Rio, but there is a huge mass of people who are being ignored. They are human beings. That's our message," says Paulo Isidora.

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