Norman, I'm sure you saw that the songs in mp3 can be downloaded from "Descargar" > "Himnos y canciones". The Altavoz del Frente site crashed down and was unavailable for many long months. Some pages aren't still re-built so far (or however you say it!)

There's an article in Revista de Folklore (in Spanish only) about the recording. Btw, this is a very interesting Spanish magazine, you can read them all on line, from #0 in 1980 up to now. They don't say anything about who was in la Cobla de Barcelona. I suppose it's just like the recordings by the "Tuna de Córdoba" or "Red Army Choir": they don't give the names of the singers/players.