The digital era (1975 to 2016)[edit]
The fourth and current "phase", the "digital" era, has seen the most rapid, dramatic and far-reaching series of changes in the history of audio recording. In a period of less than 20 years, all previous recording technologies were rapidly superseded by digital sound encoding, which was perfected by the Japanese electronics corporation Sony in the 1970s. Unlike all previous technologies, which captured a continuous analogue of the sounds being recorded, digital recording captured sound by means of a very dense and rapid series of discrete samples of the sound. When played back through a digital-to-analogue converter, these audio samples are recombined to form a continuous flow of sound. The first all-digitally-recorded popular music album, Ry Cooder's Bop 'Til You Drop, was released in 1979, and from that point, digital sound recording and reproduction quickly became the new standard at every level, from the professional recording studio to the home hi-fi.
Although a number of short-lived "hybrid" studio and consumer technologies appeared in this period (e.g. Digital Audio Tape or DAT, which recorded digital signal samples onto standard magnetic tape), Sony assured the preeminence of its new digital recording system by introducing, together with Philips, the most advanced consumer audio format to date — the digital compact disc (CD). The Compact disc rapidly replaced both the 12" album and the 7" single as the new standard consumer format, and ushered in a new era of high-fidelity consumer audio — CDs were small, portable and durable, and they could reproduce the entire audible sound spectrum, with unrestricted dynamic range, perfect clarity and no distortion. Because CDs were encoded and read optically, using a laser beam, there was no physical contact between the disc and the playback mechanism, so a well-cared-for CD could be played over and over, with absolutely no degradation or loss of fidelity. CDs also represented a considerable advance in both the physical size of the medium, and its storage capacity — LPs could only practically hold about 50 minutes of audio, because they were physically limited by the size of the disc itself and the density of the grooves that could be cut into it — the longer the recording, the closer together the grooves and thus the lower the overall fidelity; CDs, on the other hand they were less than half the overall size of the old 12" LP format, but offered about double the duration of the average LP, with up to 80 minutes of audio.