Krautrock 'supergroup' Harmonia had a relatively short life-span, but made up for this in the quality of what they did. Michael Rother's rockier approach beefed up the ambient noise-fields of Moebius & Roedelius (Cluster) who in turn gave the guitarist more sympathetic support and space than his argumentative Neu-colleague Klaus Dinger.
The 2 official albums 'Musik von Harmonia' and 'Deluxe' are both excellent examples of 70's space-rock experimentation. Brian Eno was deeply impressed by their work (as was Bowie) and travelled to Germany where several sessions were recorded, these later appeared as the 'Tracks and Traces' album.
An interesting artefact has recently fallen through my letterbox, the CD 'Documents 1975'. Harmonia played a couple of concerts in 1975 in Hamburg with Guru Guru (great psychedelic freak-out unit) drummer Mani Neumeier. They always had a Revox A77 tape machine running to record gigs for their own use and promised a fan (a collector of rare recordings) to send him a couple of live tracks - to his surprise he received a high-quality reel-to-reel tape with two live tracks and two unreleased studio numbers. Years later Michael Rother got in touch and asked if he still had any Harmonia material in his collection, he remembered this tape, dug it out of the archive and found that it was still in perfect condition.
Harmonia - Documents 1975
It is a short disc, just over 30 minutes, but what you get is some superb ambient rock that makes you wish that they had gone on to do more. There are apocryphal tales that Harmonia almost appeared on Bowie's 'Heroes' album and Eno went on to record two full albums with Cluster, who never quite broke through in the way that Kraftwerk did.
So much good music - so little time ...