"Math-metal" pioneers Watchtower, from Texas, took the concept of time-changes to a new level, combining thrash metal, syncopation and prog in their albums "Energetic Disassembly" (1985) and "Control and Resistance" (1989), giving rise to an extremely technical approach based on the rhythmic deconstruction typical of jazz fusion.This same type of prog metal will be later integrated into death metal by American bands such as Atheist (1991's "Unquestionable Presence").