BBC PAG/1/01 portable frequency generator, 1948. Orchestral 'A' portable generator, international model. Provides a consistent musical note at an a 'A' pitch, similar to that of an oboe, at a frequency of 440 Hz.

Portable frequency generator BBC PAG/1/01. Orchestral ‘A’, international model.

Portable frequency generator used to produce the ‘A’ pitch reference, used by the BBC for orchestral and instrumental tuning consistency between recordings.

Orchestras are tuned to concert pitch, ‘A’ or 440 Hertz. The reference note is commonly produced by the oboe, because the oboes is easy for the other musicians to hear, has a more stable tone than the stringed instruments in the orchestra, and is more difficult to retune. IT therefore makes sense for the rest of the orchestra to tune to the oboe.

In a live performance the ensemble can relatively easily retune if the reference instrument changes tone. In recording, consistency is required between different takes and multiple sessions, to allow for editing. This electrical generator provides an even, reliable pitch across multiple sessions. The device is programmed to fail completely if the tone it produces changes, so it is impossible to tune the ensemble to the “wrong” note.