Klem stands for 'Klub Liefhebbers Elektronische Muziek', a dutch fan group for all things synth and cosmic, organising occasional events. In 1986 they already existed 25 years and released this cassette with unreleased (as it says on the cover) music by Age, Ashra, Neuronium, Walter Rothe, Robert Schröder, Klaus Schulze and Tangerine Dream. It was solely for sale for members of their Klub. They also did a fanzine/magazine, which I would love to read again. I don't have any.