Originally surfacing as part of 1971-1981, the mammoth nine-disc box set anthologizing the first decade of influential German duo Cluster, Konzerte 1972/1977 was given a stand-alone release in 2017. The first half of the recording is a rare document of the duo's early performances at Hamburg venue Fabrik, recorded during the same year as Cluster II, which also included an excerpt from a concert at the same venue. Dieter Moebius and Hans-Joachim Roedelius would reportedly perform for six hours at a time, so it seems like a 20-minute excerpt would barely scratch the surface, but it does a fantastic job of presenting the fearless explorers working in their element. As with their earliest albums, this is a deep space odyssey that sounds entirely removed from the conventions of rock music, yet it's too aggressive and distorted to be dubbed ambient music (a term that hadn't even been coined yet). Near the beginning, there are factory-like distorted repetitions and jarring high-pitched oscillations, predicting so much of the industrial and techno that would surface during the coming decades. It only proceeds to become harsher and more hallucinatory. Even when it gets quieter, and at some points almost deathly still, it doesn't come close to sounding relaxing. The second half of this release moves ahead in time to 1977, after Cluster had released more accessible (but still visionary) albums like Zuckerzeit and Sowiesoso, and were collaborating with musicians such as Brian Eno, Can's Holger Czukay, and Asmus Tietchens. Recorded at the Festival International de la Science-Fiction in Metz, the set is closer to the earlier performance than the pretty melodies and clean sound of the albums they had been producing around that time. There's much more of a warm drone to this set, but the recording quality is grainy rather than polished, and it becomes darker and more ominous during the second half. Roedelius' hypnotic piano triplets surface, but it doesn't seem like it's getting brighter, even if it's a bit softer. Both sets are stunning, and while this might not be the best place to start with Cluster, it's a must-listen for anyone interested in their more abstract side.