Atrium Musicae was founded in 1964 and they were four brothers (Gregorio (1944) Eduardo, Carlos and Luis Paniagua and then Beatriz Amo, Christina Ubeda and Jesus Greus. other memembers were Pablo Cano and some others.
I found one video of 1977
The first recordings were the following ,which were later become known under the Colleccion de Musica Antigua Espanola, 5 cds all produced by Robert Pla.
1968 Cantigas de Santa Maria, El Sabio
1968 Musica en Catalonia XIV siglo
On this recording were playing;Marcel Moreiras, Christine Garcia, Mariano Martin, Eugenio Urbina, Javier Coello and then Gregorio, Eduardo, Carlos and Carmen (sister?) Paniagua.
1969 Monodia Cortesana Medieval /Musica Arabigo Andaluza
1970 Codex Huelgas
1971 Missa Barcelona (not part of the 5 cd's)
1976 MÚSICA IUCUNDA .SIGLOS XII AL XVII
1976 MUSIQUE ARABO ANDALOUSE
1977 DIEGO ORTIZ RECERCADAS
Pablo Cano, Beatriz Amo, Christina Ubeda and Gregorio, Eduardo , Luis and Carlos Paniagua
1978 MUSIQUE DE LA GRECE ANTIQUE
1978 THIBAUT DE NAVARRE
1978 Codex Gluteo
Begona Olavide seems to have replaced Christine Ubeda on this album
1980 LA SPAGNA -XV-XVI-XVII Centuries
With Christine Ubeda again, but also with Jacob du -ran-Loriga and Rosalia Peraita and Maximo Paradera and then only Gregorio and Eduardo
1981 with Lucia Bose ;lo Pomodoro
1981 los indias des espana
1982 LA FOLIA- DE LA SPAGNA
With Daniel Del Rio, Andre Prittwitz and Albertina Do Huette and then Gregorio, Luis and Eduardo Paniagua
Spectacles for tribuffalos