The world's oldest known recording of computer-generated music has been restored to its former glory by a team from the British Library. Taken from an acetate-cut recording made by the BBC in 1951, the selection of three songs generated by the University of Manchester's Computing Machine Laboratory's Ferranti Mark I computer was recently restored with the help of a programming manual written by Alan Turing.

The oldest recording of computer music was made in late 1951 by a BBC outside broadcast unit at the University of Manchester for the BBC Home Service program Children's Hour. The rough two-minute recording is of the Ferranti Mark I computer playing "God Save the King", "Baa Baa Black Sheep", and the popular swing-band hit "In the Mood." The recording was made on mobile recording equipment and etched into a 12-inch, single-sided acetate disc, as was normal for the time.

Computer music goes back much farther than most people realize. The famous "Daisy Bell" rendition by an IBM 704 computer at Bell Labs in 1961 is credited as the first example of a computer singing, but it's far from the first music-making computer. That honor goes to Australia's first digital computer, CSIRAC, which played "Colonel Bogey" in early 1951 weeks before the Ferranti Mark I, but that was never recorded.

The acetate disc was saved by Manchester University engineer Frank Cooper(Credit: Chris Burton/British Library)

The oldest known musical notes from a computer were the work of the famous computer pioneer Alan Turing. In late 1948, Turing had taken over as head of the Computing Machine Laboratory, which was developing the Manchester Mark I computer. He noticed that the loudspeaker or "hooter" on the Mark I could be made to produce short bursts of sound, which when repeated many times per second in particular patterns, created different musical notes. Turing didn't seem very musically minded, so the hooter was relegated to sounding system alerts – such as when the computer completed running its program, or if an error occurred – and the feature continued in later designs.

The Mark I acted as the prototype for the Ferranti Mark I (also known as the Manchester Ferranti or the Manchester Mark II). This was a commercial version of the previous Manchester Mark I and was developed by Tom Kilburn, who designed and built the computer with Freddie Williams.

The room-sized Ferranti Mark I was already one for the history books. It was the first computer that could store a program using a 512-page magnetic drum, and one of the first computers to play chess. However, it was still very primitive by modern standards with only 4,050 radio valves and no operating system. Instead, it was programmed using machine language punched onto paper tape.

Christopher Strachey sunbathing in the garden of his cottage 'The Mud House' in 1973(Credit: Bodleian Library/Camphill Village Trust/British Library)

Music came to Manchester thanks to Christopher Strachey – another major computer pioneer and former maths master at Harrow. In 1951, he was invited to Manchester by his friend Turing to have a go at the Ferranti Mark I.

Using Turing's Programmers' Handbook for Manchester Electronic Computer Mark II, which he'd borrowed from turing earlier in 1951 and is credited as the first programming manual, Strachey programmed the computer to play a game of noughts and crosses using the longest computer program yet written. This required his working at an all-night session of the sort that has since become all-too familiar to computer programmers, but was necessary at Manchester because so much time was booked on the computer during the day that most programming had to be done after hours.

The game playing was an already interesting feat, but what caught onlookers' attention was that when the computer terminated its task, Strachey had programmed it to use the hooter function in such a way that the machine played "God Save the King".

Strachey went on to write a more general program to allow others to write music for the Ferranti Mark I and in October 1951 the BBC came to make a recording of the remarkable machine. Using field equipment, a crew recorded the three songs and a copy was given to university engineer Frank Cooper at his request – one of the two that survives. But when the recording resurfaced decades later, it was found to be badly out of pitch and very much in need of restoration.

Jack Copeland and Jason Long  carried out the restoration for the British Library(Credit: British Library)

The problem was that when a team from the British Library took on the task, they found themselves at a bit of a handicap. For one thing, the Ferranti Mark I no longer exists. After the project folded in 1952 and the computer was sold to the University of Toronto and was scrapped years ago. So how could the team restore the original pitch of a recording where the "instrument" is no longer available to show what it should sound like?

On top of that, the computer wasn't exactly a grand piano. It couldn't hit the notes properly in the first place and could only approximate the desired pitch. However, by referring to Turing's manual, the British Library team did come up with a workaround to calculate what sound the computer could produce, which gave them a starting point.

A computer frequency analysis of the original recording showed that the frequencies were badly skewed to the point where it sounded nothing like it should, and would have been impossible for the computer to make in the first place. By using these impossible pitches as a benchmark and comparing them to what they knew the computer could generate, the team found that the recording was playing at the wrong speed – a common problem when recording audio on field equipment of the day. To make the recording properly audible, it had to be sped up, extraneous noise filtered out, and digitally pitch-corrected to remove wobbles.

The result is a recital of computer music not heard properly for over half a century. It also reveals a temperamental artist that had to be coaxed to perform. As the Manchester technicians struggled to get the computer cooperate in 1951, a female voice on the recording can be heard saying: "The machine's obviously not in the mood."

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