One of music’s most powerful attributes is its ability to bring people together around a cause, a theme Bill has explored many times with a variety of artists. Below, we’ve excerpted four of those conversations — with Pete Seeger, Bernice Johnson Reagon, Johnny Cash and Tom Morello — which delve deeply into music’s power to inspire, unite, and strike a common chord.

Along with his friend Woody Guthrie, Pete Seeger is credited for sparking the folk music revival that swept America in the 1960s and played a role in the social movements that gained traction during that decade. In this clip, Seeger tells Bill how music has a power that, even after decades of playing it, he still doesn’t fully understand.

Bernice Johnson Reagon — singer, civil rights activist and scholar — was an integral part of the African-American struggle for civil rights. Along with Cordell Reagon, Rutha Harris and Charles Neblett, Bernice founded the Student Nonviolent Coordinating Committee (SNCC) Freedom Singers, the first group of freedom singers to travel nationally. In this excerpt from a 1991 interview, Reagon explains to Bill how music was used throughout black history to empower and show solidarity.

One of the many things Johnny Cash is remembered for are his prison performances, during which he showed a heartfelt empathy for inmates. At Huntsville State Prison in 1957, Cash’s performance of “Amazing Grace” held special potency for crowds of convicted felons. In this 1990 clip featuring both conversation and performances, Cash and Huntsville prisoners explain the common message that “Amazing Grace” holds for them.

Like Woody Guthrie (whose guitar was famously inscribed with the slogan “This Machine Kills Fascists”), former Rage Against the Machine guitarist Tom Morello uses his instrument to “steel the backbone of people on the frontlines of social justice struggles.” In this clip from his May 2012 conversation with Bill on Moyers & Company, Morello explains the role of music in uniting a movement.