What makes Cantigas do Maio by José Afonso notable?

'Cantigas do Maio' is celebrated for its influential role in the Portuguese cultural landscape, particularly during the Carnation Revolution. The track 'Grândola vila morena' became an anthem for the revolution, symbolizing resistance against oppression and helping to inspire change in Portuguese society. Released in 1971, 'Cantigas do Maio' was José Afonso's third album, following his notable works that established him as a leading voice in Portuguese folk music. At this time, the country was under a dictatorship, and Afonso's music began to resonate deeply with the growing anti-fascist sentiments among the populace, solidifying his role as a protest singer.