Music speaks volumes. That’s a message John Legend and Columbian musician Juanes underlined outside Arizona’s Eloy Detention Center, where they led a campaign against mass incarceration in the United States as well as the ongoing issues on immigration.

The Grammy winners performed two of their respective hits and a duet of Bob Marley’s “Redemption Song” for dozens of people outside the facility.

“The reason why we’re here, one, is because we want to bear witness to what’s happening so we could tell the world about it,” said John Legend.

The concert was broadcasted on ABC’s “Good Morning America.”

“It’s very hard to understand that someone is deprived of their freedom unjustly, and that’s why we’re here with out music,” Juanes explained.

Activists were part of the audience during the show, along with relatives of detainees. Inmates were not let out of their cell to hear the concert.

In a statement regarding the this, U.S. Immigration and Customs Enforcement said it was “committed to ensuring the safety and welfare of all those in its custody.”

About 1,500 detainees are being held in Eloy.

“This afternoon, residents of the Eloy Detention Facility’s south side were confined to their cells and residence pods for approximately one hour after concerns arose that an unsanctioned concert being conducted within view of the center’s south recreation yard might provoke a disturbance. The decision to briefly restrict residents’ movement was made out of an abundance of caution for both detainees’ and employees’ safety,” the statement continued.

The rare performance brings great awareness to an issue that is often dodged or overlooked altogether in the media.

Read more from the performance here.