Carles Santos began his formal musical education at the prestigious Conservatori Superior de Música del Liceu in Barcelona. There, he received awards that gave him the opportunity to continue his studies in Paris, where he worked with Jacques Fèvrier, Robert Casadesus, Magda Tagliaferro, and Marguerite Long, among others. Later he studied with Harry Datymer in Switzerland. In 1961, he began his career as a pianist, with a repertoire that included works by Béla Bartók, Arnold Schönberg, and Anton Webern. During these years, he also played the musical parts of Joan Brossa's Concert Irregular, which premiered in Barcelona and New York as part of the commemoration of the 75th birthday of Joan Miró. A grant awarded by the Juan March Foundation in 1968 allowed Santos to move to the United States, where he met and worked with a number of avant-garde artists, principally Philip Corner and including John Cage.
In the late 1960s, Santos turned his attention to the production of films, and his oeuvre in this discipline eventually grew to include short films, full-length films, documentaries, and videos. Over the years, he collaborated with such directors as Pere Portabella, Jordi Cadena, and Carles Durán. His own first short film, L'Apat, premiered in 1967.
During the 1970s, Santos increasingly devoted himself to performing his own compositions, and eventually he decided to play them exclusively. His compositions are decidedly minimalistic and at the same time bear the stamp of romantic, traditional Spanish, atonal, and 12-tone music. In these years and into the 1980s, he took part in a number of important musical events, including the Festival d'Automne in Paris, the Musicalia in Milan, the International New Jazz Festival in Moers, Germany, the Biennial in San Juan, Puerto Rico, the Zürcher Theater Spektakel in Zurich, the Music Theatre Festival in London, Wintermusik '82 in Karlsruhe, Germany, and New Music America '83 in Washington, DC. In his performances, his goal was to avoid the boredom often caused in the audience by certain avant-garde music.
Sydney Opera House, the Hebbel-Theater in Berlin, and the Palau de la Música Catalana in Barcelona. His musical shows are marked by extravagance, sexual themes, and deliberate provocation, with the goal of questioning established concepts, albeit with a sense of humor. The notes to the 2006 exhibition of Santos's costumes held in Barcelona at the Museu del Tèxtil i la Indumentaria (Mariaelena Roqué desvesteix Carles Santos [Mariaelena Roqué Undresses Carles Santos]), indicate that Santos, through his shows, is expressing his loves and fears and attempting to banish his personal demons.
Santos has been commissioned to compose works for a variety of special occasions, including the opening ceremonies of the 1992 Summer Olympic Games in Barcelona and the opening of the 2001 Biennial of Arts in Valencia.
A major retrospective of Santos's works titled Visca el Piano (Long Live the Piano) was held in 2006 at the Fundació Joan Miró in Barcelona. The exhibition included videos of his scenic musical shows, graphic and photographic works, montages, and kinetic sculptures. The last category included a waltzing player piano that whirled around the exhibition hall under its own power while playing music by Bach and somehow avoiding running into the other exhibit.