Which instrument is commonly associated with American Folk music?

The banjo is commonly associated with American folk music due to its historical roots and cultural significance. It originated in African American communities and became a staple in various folk traditions across the United States, particularly in Appalachian and Southern music. The unique sound of the banjo, characterized by its bright, sharp tones and rhythmic strumming, contributes to the upbeat and lively nature of folk music. It has been featured in numerous folk songs and has played a significant role in its development, especially in bluegrass music, which is a subset of folk music. This connection to the roots of American folk traditions solidifies the banjo's place as an iconic instrument within the genre.

The other instruments listed, while they may have been used in various folk contexts at times, do not have the same direct association with the core elements and styles of American folk music as the banjo does.