The Spanish Civil War spawned a huge number of songs, particularly on the Republican side. Many of these are available online; there are also a number of songbooks. A classic is the Anarchist hymn “A las barricadas”: classic version / modern version (Ana Belén & Víctor Manuel).
This website lists songs, with audio files, dividing Nationalist from Republican songs.
Songs from the Lincoln Brigade were made famous by Pete Seeger, Tom Glazer, and Woody Guthrie:
- Pete Seeger & The Almanac Singers: Si me quieres escribir
- Pete Seeger & The Almanac Singers: Viva la Quince Brigada
- Pete Seeger & Arlo Guthrie: Jarama Valley
- Pete Seeger and friends: Viva la Quince Brigada
In 2014, the Smithsonian re-issued its legendary collections Songs of the Spanish Civil War. See this essay by Peter Glazer.