After the advent of microphones and electronic amplification, the next technical revolution in sound recording came with the introduction of magnetic tape recorders. The technology of magnetic recording dates back to 1898, when Valdemar Poulsen patented the Telegraphon, a device that recorded the electrical audio signal from a telephone transmitter as variations in magnetic flux on a length of steel piano wire. Over the next thirty years the technique evolved very slowly. By 1930, however, advances in electronics allowed the first commercially successful wire recorders to be introduced as dictating machines and telephone recorders in Europe and North America. Recording on solid steel media, whether wire or tape, remained the dominant form of magnetic recording outside Germany until about 1950. Perhaps the most interesting recorder of this type was the Blattnerphone, or Marconi-Stille recorder. This large device, which recorded on solid steel tape three millimetres wide, was developed in Germany and sold to several radio broadcasters, including, in 1935, the forerunner of the Canadian Broadcasting Corporation.
At around the same time that the Blattnerphone was introduced, other German researchers were perfecting a method of coating thin celluloid tape with iron oxide particles. This arrangement was not only much lighter and more compact than solid steel or wire, but the particles were actually more easily magnetized. After the Second World War, American manufacturers introduced copies of these German Magnetophons. While the first such device, the Brush BK-401 was designed as a home recorder, broadcasters and record companies soon began to buy large numbers of such professional models as the Ampex 300. Not only were these machines capable of very high fidelity and low noise performance, but they could record long passages without interruption. Moreover, errors could be corrected or diverse programs assembled simply by splicing in the desired material. Beginning in the 1950s, recording engineers also discovered that by overdubbing or by recording on multiple tracks, they could assemble an ideal performance without the need for recording an entire ensemble in a single, flawless, nerve-wracking take.
Except among audiophiles, consumer acceptance of open-reel recorder-players was initially limited by their bulk and relative complexity. With the gradual spread of the transistor, solid state components began to replace heavy and power hungry vacuum tubes. As well, manufacturers developed various cassettes and cartridges to simplify tape operation. One, the 8-track cartridge, was very popular from the mid-1960s to the mid-1970s. In 1963, Philips introduced the "compact cassette." Initially the cassettes were used in office dictating machines, but by 1970 cassette recorders were being employed by a wide variety of professional and home users. During the 1970s, the quality of cassette recordings was improved to the point where they became acceptable for music listening. Cassette "decks" were included by many manufacturers in stereo components but the portable aspect of cassette players was not forgotten. In 1980, Sony introduced the Walkman, a headphone-equipped "personal" stereo that could be held in the palm of the hand and played anywhere. Soon after, manufacturers also began to build portable stereos or "boom boxes" that coupled a cassette player with a more powerful amplifier and speakers.