EMI BTR-2 tape recorder (No. 1), 1952.

The BTR-2 was EMI's first major success in broadcast tape recorder manufacturing. A mono, valve machine - versions were made to run at various speeds (the capstan had to be changed) from 7 1/2 ips to 60 ips. They provided the bulk of BBC tape recordings in the 1950s, and were still in use well into the 1970s. Beginning with the BTR-1 in 1947, the BTR (British Tape Recorder) machines were the first magnetic tape recorders to be manufactured in Britain. Their design imitated that of the magnetic tape recorders used by the Germans during the war. Because these multi-track recorders were painted EMI green, they then became known as the "Green Machines". Studio engineers devised clever ways of creating audio effects by manipulating the BTR-2 recorder functions. This created echo, and 'flanging' effects. The BTR-2 was responsible for many of the psychedelic effects of the late 1960s.