Octavarium is Dream Theater's eighth studio album, released in 2005, which is built around the concept of an octave, with eight songs, each in a different musical key, starting with F and creating a continuous musical loop that ends where it begins. The album serves as a celebration of the band's influences and a culmination of their creative output, featuring a diverse range of styles from their progressive metal roots to simpler, arena-rock-inspired songs, all anchored by the epic 24-minute title track, "Octavarium".