Ernst Busch was born into a working-class family in Kiel - where I now live - in 1900, trained as an actor and rose to fame in pre-war Berlin. By then he'd become a member of the Communist Party. For his Communist convictions and his singing of material by Brecht and Eisler, Tucholsky and others, as well as traditional workers' songs (I have several of his recordings) he became known as the "Tauber of the Barricades" (Richard Tauber being a famous opera singer of the same era). He had to flee the Nazis, went to Spain to sing to the Republican troops, lived in the Netherlands for a while until (in 1944?) he was discovered and transported back to Berlin. He only survived because the Allies were faster than his trial.
After the war he stayed in what was to become the GDR, where he managed to be both a treasured icon and a thorn in the side of the authorities. He founded the 'Amiga' record label and recorded extensively for them, was 'frozen out' by the political elite for some time, and lived till 1980. I have a biography of him (in German) - I'll post the details if it's any good to you. In recent years a label (Buschfunk?) has started bringing out his recordings on CD. Have you tried a search engine?