This is the most readily available collection of the recordings made by the influential Almanac Singers, including the title track, “The Union Maid,” “Which Side Are You On,” and other standards of the union struggle. Pete Seeger’s idea for a folk group would take more permanent form a decade later with the Weavers, and the concept would help give birth to the folk boom of the late 1950s and early ’60s. But it was all here in the simple instrumentation and vibrant harmony singing of the Almanacs. This is one of the essential recordings of American folk music. Note, however, that the album contains only six Almanac Singers tracks, recorded in May 1941, paired with seven tracks recorded in 1955 by Pete Seeger and a chorus dubbed “the Song Swappers” that included Erik Darling, later of the Weavers, and Mary Travers, later of Peter, Paul and Mary. – William Ruhlmann