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.
A Spanish-Civil-War-inspired song that became very popular in the United States–witness this oral history project (video) by James D. Fernández and Katie Halper–was “No Pasarán” (audio).
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.