For our 406 project promoting aural literacy, the Boston Soy Bean Police chose to focus on music, specifically, American music that calls for social change. We also found relevant information by googling subversive music and protest music, but technology shaped our project from its inception by dictating the search terms that yielded the most fruitful research.
Protest music has a long tradition in America, we could have started before the Revolutionary War, when the British derisively referred to the colonists as "Yankee Doodle Dandies." Rather than let the slur get them down, the colonists adopted the anthem and marched into battle against the British to the tune originally meant to belittle them. Another era rich in subversive music was the Civil War, when slaves used songs to send coded messages about escape and freedom. Included in the links section are some excellent sites that allow the interested reader to explore the protest music from those turbulent times.
Our project focused on music that was from the mid 20th century onward, for brevity's sake.