Cluster were a German musical duo consisting of Hans-Joachim Roedelius and Dieter Moebius, formed in 1971 and associated with West Germany's krautrock and kosmische music scenes. Born from the earlier Berlin-based group Kluster, they relocated in 1971 into the countryside village of Forst, Lower Saxony, where they built a studio and collaborated with musicians such as Conny Plank, Brian Eno, and Michael Rother; with the latter, they formed the influential side-project Harmonia. After first disbanding in 1981, Cluster reunited several times: from 1989 to 1997, and from 2007 to 2010.
AllMusic described the group as "the most important and consistently underrated space rock unit of the '70s." Music historian Julian Cope places three Cluster albums-Cluster II, Zuckerzeit, and Sowiesoso -in his Krautrock Top 50 and The Wire places the debut album in its "One Hundred Records That Set the World on Fire".