If you are a fan of music, and of musical media in particular, you may have heard the story that CDs lasted 74 minutes to contain Beethoven’s Ninth Symphony. For decades it was believed that the Compact discor CD, would have lasted 74 minutes because Norio Ohga, president of Sony and classical music enthusiast, wanted the Ninth Symphony by Beethoven — in its longest version, the one conducted by Wilhelm Furtwängler in 1951 — could be listened to without interruption on a single disc. A fascinating story, sure, but not entirely true. The companies involved, Philips and Sony, had engineering, logistical and commercial needs that went far beyond Ohga’s passion for Beethoven. It is plausible that the symphony played a symbolic role in the decision-making process, but it was not the real reason for the standard length of 74 minutes and diameter of 12 centimeters. The reasons, as we will see, are to be found in the collaboration between two electronic giants, in the physical limits of the optical technology of the time and even in the practical consequences of an increase of a few millimeters in the diameter of the disk.
What is the maximum length of a CD: minutes
In the early 1970s, Philips engineers were working on a 30 centimeter diameter video disc capable of holding an hour of analog film. The project was a technical success on the one hand, but a commercial failure on the other. However, from that experience the idea of adapting the same technology for a support dedicated only to digital audio was born. Lou Ottens, technical director of Philips’ audio division – for the record, the same person who had created the compact cassette in the 1960s – asked to develop a record that could offer superior sound quality compared to vinyl and cassettes. The first prototypes appeared in 1976 and worked well, but the question of size remained open. Ottens imagined an 11.5 centimeter disc, the same diagonal as an audio cassette, thinking that the visual parallelism could favor the success of the new format.
When in 1979 the technological giants of the time Philips and Sony decided to collaborate to define a single standard for the “digital audio disc”, a crucial phase of technical negotiations began. The joint group of experts, met several times between Eindhoven and Tokyo, had to establish fundamental parameters: the quality of the sound, the error correction code (i.e. the mathematical system that would allow the player to compensate for any defects in the surface of the disc), the diameter and, consequently, the playback duration. Sony initially proposed a 10 centimeter disc, more compact and suitable for future portable players. Philips, for its part, insisted on the 11.5 centimeter format already ready for industrial production. The final choice, established in December 1979, was a sort of compromise: 12 centimeters in diameter and 74 minutes of musical playback.
The myth of Beethoven on the 74 minutes contained in a musical disc
And it is precisely at this point in the story that the myth of Beethoven comes into play. According to the “official story” later told by Philips and taken up by many media over the decades, Ohga explicitly asked that a CD could contain the entire Ninth Symphony. To obtain those 74 minutes and 33 seconds, it was necessary to increase the diameter of the disk from 11.5 to 12 centimeters. But, as Kees A. Schouhamer Immink – one of the Philips engineers who directly participated in the development of the technology – would tell several years later – things didn’t go exactly that way.
In one of his articles published on Nature ElectronicsImmink explains that the legend was born more as a sort of romantic anecdote to accompany the true history of the birth of the CD. At the time, in fact, it had not yet been decided which digital modulation code to use for reading the data. A few months later, Immink himself developed a new system, called EFM (Eight-to-Fourteen Modulation), which allowed the amount of recordable data to be increased by 30%. With that technology, even a 10-centimeter disk could have contained a complete Ninth Symphony.
The “romantic-symphonic” version of the story, therefore, was probably a narrative strategy to give a human face to a purely technical decision. Toshitada Doi, Sony’s principal engineer, would confirm this many years later. In his article, in fact, Immink said:
In October 2017 I had a conversation during lunch at the Takanawa Prince Hotel in Tokyo with my adventure companion, Sony’s top engineer, Toshitada Doi, who, when I told him about my doubts about Beethoven’s story, said: «You’re right, of course, but it was a good story, wasn’t it?».
