of popular albums were released in one of the competing four-channel formats; among the best known are Mike Oldfield's Tubular Bells and Pink Floyd's The Dark Side of the Moon. Quadraphonic sound was not a commercial success, partly because of competing and somewhat incompatible four-channel sound systems (e.g., CBS, JVC, Dynaco and others all had systems) and generally poor quality, even when played as intended on the correct equipment, of the released music. It eventually faded out in the late 1970s, although this early venture paved the way for the eventual introduction of domestic surround sound systems in home theatre use, which gained popularity following the introduction of the DVD. Audio components The replacement of the relatively fragile vacuum tube by the smaller, rugged and efficient transistor also accelerated the sale of consumer high-fidelity sound systems from the 1960s onward. In the 1950s, most record players were monophonic and had relatively low sound quality. Few consumers could afford high-quality stereophonic sound systems. In the 1960s, American manufacturers introduced a new generation of modular hi-fi components — separate turntables, pre-amplifiers, amplifiers, both combined as integrated amplifiers, tape recorders, and other ancillary equipment like the graphic equalizer, which could be connected together to create a complete home sound system. These developments were rapidly taken up by major Japanese electronics companies, which soon flooded the world market with relatively affordable, high-quality transistorized audio components. By the 1980s, corporations like Sony had become world leaders in the music recording and playback industry. Digital The advent of digital sound recording and later the compact disc (CD) in 1982 brought significant improvements in the quality and durability of recordings. The CD initiated another massive wave of change in the consumer music industry, with vinyl records effectively relegated to a small niche market by the mid-1990s. The record industry fiercely resisted the introduction of digital systems, fearing wholesale piracy on a medium able to produce perfect copies of original released recordings. The most recent and revolutionary developments have been in digital recording, with the development of various uncompressed and compressed digital audio file formats, processors capable and fast enough to convert the digital data to sound in real time, and inexpensive mass storage. This generated new types of portable digital audio players. The minidisc player, using ATRAC compression on small, re-writeable discs was introduced in the 1990s, but became obsolescent as solid-state non-volatile flash memory dropped in