Many studios later purchased ex-BBC units, so quite a few were found in non-EMI London studios. The BTR3 recorder was initially intended to support 2 or 4 tracks, but the only machines produced were the stereo (2-track) machines, the 4-track version having been rejected at the prototype stage. Only a few of these BTR3s were built, and the only known use of them is at the Abbey Road Studios during the 1960s, where they were used for all stereo recording and disc mastering.
Several studios later purchased former BBC units, leading to many being found in non-EMI London locations. The BTR3 recorder was initially intended to support 2 or 4 tracks but only produced models were stereo (2-track) machines; the 4-track version was rejected at the prototype stage. Only a few of these BTR3s were built, and their sole known use involved Abbey Road Studios in the 1960s for all stereo recording and disc mastering.