Canto Livre

This is a kind of music with roots in Alentejo music, predominantly inspired by political messages, in particular from left-wing thinkers. It was very common after the 1974 carnation revolution

Carnation Revolution

The Carnation Revolution , also referred to as the 25 de Abril , was a military coup started on 25 April 1974, in Lisbon, Portugal, coupled with an unanticipated and extensive campaign of civil resistance...

in Portugal, since the country had liberated from an almost 40 year right-wing dictatorship. Nowadays it is not heard much, although the term "canto livre" can also mean a gathering of singers which perform freely without charging for their show.