Aggrotech is an evolution of electro-industrial and dark electro with a strong influence of techno music that first surfaced in the mid-1990s, but has been revitalized in recent years. Also referred to as "Terror EBM", and more recently referred to as "Hellektro", its sound is typified by somewhat harsh song structures, aggressive beats and lyrics of a militant, pessimistic or explicit nature. Typically, the vocals are distorted to sound hoarse, harsh and without tone. Artists also frequently use atonal melodic structures.