Songfacts®:

• "Arto" is System Of A Down's version of the Armenian hymn "Der Voghormia," which translates to "Lord Have Mercy" and is traditionally played at funerals as a prayer for the dead. It's titled "Arto" because their friend Arto Tuncboyaciyan played on it.
  
  The song is a chant, with the band playing Armenian instruments; Tuncboyaciyan played a reed instrument called a duduk.
• System Of A Down released this song to acknowledge the Armenian genocide that killed about 1.5 million starting in 1915. The band has worked tirelessly to bring attention to the genocide, which they feel has been forgotten in most of the world.
• On streaming services, "Arto" appears as Track 15 on the Toxicity album, but on the CD it was a "hidden track," not listed on the tracklist. Unlike most hidden tracks, which often appear after minutes of silence, it wasn't hard to find, coming on just seconds after the last listed song, "Aerials."