In 1958, during Portugal's dictatorial Estado Novo regime, he was imprisoned for 18 months for joining the Portuguese Communist Party, at the time an illegal organization.

He worked in the radiography archive of the Hospital de São José, in Lisbon, while maintaining his musical career.

[2] Paredes grew up in an environment of discreet resistance and political opposition to António Salazar's Estado Novo regime.

[2] In the morning of 26 September 1958, he was arrested by PIDE agents in his workplace in Hospital de São José, on the accusation of belonging to an illegal political party opposing the government.

[3] According to some sources, people in the prison thought that Paredes was going insane, walking around his cell pretending to play the guitar, when in fact he was composing.

[4][5] After his release from prison, he was suspended from his job in the hospital and worked for some years as a delegate of medical propaganda.

[2] After the Carnation Revolution in Portugal, like others who had been political prisoners during the Estado Novo regime, Paredes was seen as a hero.

The piece "Canção Verdes Anos", which is part of this soundtrack and was also included in his first studio album, became one his most recognizable works.

He also composed the soundtracks for the film Fado Corrido (1964), by Jorge Brum do Canto, the film Mudar de Vida (1966), by Paulo Rocha, and contributed to the soundtrack of several short-films: Rendas de Metais Preciosos (1960), by Cândido Costa Pinto; P.X.O.

(1962), by Pierre Kast and Jacques Valcroze; As Pinturas do Meu Irmão Júlio (1965), by Manoel de Oliveira; Crónica do Esforço Perdido (1966), by António de Macedo; À Cidade (The City) (1968) and The Colombus Route (1969), by José Fonseca e Costa; and Tráfego e Estiva (1968), by Manuel Guimarães.

[2] Between 1971 and 1977, he composed the music for Agustin Cuzzani's play O Avançado Centro Morreu ao Amanhecer, performed by the Campolide Theatre Group.

He participated in several events promoted by the Portuguese Communist Party, playing shows in Portugal and Eastern Europe.

Eventually, the initial plans for the album were abandoned, but some of the recordings from these sessions were selected by Paredes for a release named O Oiro e o Trigo.

[10] In 1986 he released a collaboration album with Portuguese composer António Victorino de Almeida, titled Invenções Livres.

He was interned at the Fundação-Lar Nossa Senhora da Saúde, in Campo de Ourique, Lisbon, until his death.

[20][21][22] The Carlos Paredes Prize, an award for Portuguese musicians given by the Vila Franca de Xira municipality since 2003, is named after him.

[23] In 1992, Carlos Paredes was awarded the title of Commander of the Military Order of Saint James of the Sword by the President of Portugal.