This LP reveals the extraordinary diversity of research - almost all hidden - by Spanish musicians in the '50s and '60s. Those pieces were composed while the country was under the tyranny of Francisco Franco. It is truly the ultimate grail, developed by musicologist Miguel Álvarez-Fernández, he is its curator, editor and commentator. This undoubtedly marks a major step in the approach and understanding of this music which had to fight to exist before the death of Franco in 1975.

Miguel Álvarez-Fernández (Madrid, 1979) is a writer. He hosts the weekly radio broadcast Ars Sonora - dedicated to sound art and experimental music, and offering hundreds of freely available podcasts on Radio Clásica (Spanish National Radio).

Jose Val del Omar (1904-1982) is essentially a creator, a filmmaker developing a dreamlike art - not without links with Federico Garcia Lorca or Luis Buñuel.

Eduardo Polonio (1941- ) between 1966 and 1970 at the Institute of Psychoacoustics and Electronic Music-IPEM of the University of Ghent, Belgium. Eduardo Polonio, has published, in forty years, more than a hundred works.

Josep Maria Mestres Quadreny (1929-2011) in 1952 he joined the Manuel de Falla Circle and in 1974 he founded the Laboratori de Música Electroacústica Phonos. During his life he collaborated with Joan Miró and Antoni Tàpies.

Juan Hidalgo (1927-2018) in 1957 he participated in the music festival XII Internationale Ferienkurse Fur Neue Musik in Darmstadt. The following year he met the American composers John Cage and David Tudor. Member of Fluxus, in 1966 he participated with Gustav Metzger, Otto Muehl, Wolf Vostell and Hermann Nitsch in the Destruction in Art Symposium in London.

Cristóbal Halffter (1930-2021) was soon considered one of the most important composers of his generation.  As a lecturer at the Internationale Ferienkurse für Neue Musik in Darmstadt, he worked with Pierre Boulez, Karlheinz Stockhausen and Luciano Berio.