I have known "Die Moorsoldaten" for a very long time. The first rendering I heard was that of the "Klingende Runde für jung und alt" adult choir under the direction of Karola Heißenbüttel in 1988. This song is extremely well known and popular (at least on the political left) here in Germany as it deals with the ultra depressing days of the concentration camps and their hapless inmates, political prisoners, prior to World War II.
That this song is now in my repertoire, at least as accompanist and bass-part singer, is due to one Nina Kreft who loves this song dearly. Our source is Lieder der Arbeiterbewegung
where there is a very graphical account of how the song came to be written and the life of the inmates. The account recalls that eventually, even the prison guards liked it so much that they enjoined the inmates to sing it when marching to their toils on around Börgermoor. The song was written in 1934 in the Börgermoor Concentration Camp in 1934 by Esser and Wolfgang Langhof.
Nina sings this song quite movingly in a soft soprano for the first five verses breaking into a triumphant high descant for the final verse. Great stuff indeed!