“A key problem facing audio archivists is how to establish the correct pitch of a historical recording. Without some independent means of knowing how the original sounded, it can be very difficult—or even impossible—to tell whether an archived recording is playing at the right pitch. An important case in point is the earliest known recording of computer-generated music. In 1951, a BBC outside broadcast unit in Manchester used a portable acetate disc cutter to capture three melodies played by a primeval computer. This gigantic computer filled much of the ground floor of Alan Turing’s Computing Machine Laboratory.
Today, all that remains of the recording session is a 12-inch single-sided acetate disc, cut by the BBC’s technician while the computer played. The computer itself was scrapped long ago, so the archived recording is our only window on that historic soundscape. What a disappointment it was, therefore, to discover that the pitches were not accurate: the recording gave at best only a rough impression of how the computer sounded. But with some electronic detective work it proved possible to restore the recording—with the result that the true sound of this ancestral computer can be heard once again, for the first time in more than half a century.”
The link directly above contians the restored recording