Os Mundi from Berlin became known because of their two LPs on Metronome and Brain. In 1975, when they had almost reached the period of breaking up, their guitarist Udo Arndt was doing a practical training in the studio of a broadcasting station and invited his friends there to make some free-of-charge recordings in order to practice. The recording sessions took place with changing line-ups, together with guest musicians, e. g. from Agitation Free. Some rather softened jazz-rock without vocals was played, which sounds very clean and has now been released for the first time. Additionally there are three other studio recordings on the CD and two RIAS tracks. In the booklet the history of Os Mundi is given in detail, with a lot of pictures, exact discographies, cover reproductions, etc. It is so to speak the missing part in the group's catalogue of works.