Octophonic sound is a form of audio reproduction that presents eight discrete audio channels using eight speakers. For playback, the speakers may be positioned in a circle around the listeners or in any other configuration.
Typical speaker configurations are eight spaced on a circle by 45° (oriented with first speaker 0° or at 22.5°), or the vertices of a cube to create a double quadraphonic set-up with elevation.  In reference to his own work, Karlheinz Stockhausen made a distinction between these two forms, reserving the term "octophonic" for a cube configuration, as found in his Oktophonie and the electronic music for scene 2 and the Farewell of Mittwoch aus Licht , and using the expression "eight-channel sound" for the circular arrangement, as used in Sirius , Unsichtbare Chöre , or Hours 13 to 21 of the Klang cycle.   While quadraphonic sound uses four speakers positioned in a square at the four corners of the listening space (either on the ground or raised above the listeners), this cubical kind of octophonic spatialization offers both horizontal and vertical sound spatialization, meaning listeners get a sense of height. In order for such movement in space to be heard, it is necessary that rhythms be slow, and pitches change mainly in small steps or in glissandos. 
Some notable composers who have worked with octophonic spatialisation include Karlheinz Stockhausen, Jonathan Harvey, Gérard Pape, and Larry Austin. The first known octophonic (that is, eight-channel) electronic music was John Cage's Williams Mix (1951–53) for eight separate simultaneously played back quarter-inch magnetic tapes.   Austin later made a surround-sound octophonic mix of Williams Mix, Williams (re)Mix[ed] (1997–2000), using the score and different sound sources.  This version is intended to be played back on eight speakers surrounding the audience in a 360° circle, using (unlike Cage's original version) stereo source recordings heard in adjacent speaker pairs.  Octophonic sound (in the general sense of eight-channel playback) was stimulated primarily by "the equal coverage it provides to all listening angles" and also by the precedence of eight-channel (initially tape) sound and subsequent ease of playback. 
The 8-track tape is a magnetic-tape sound recording technology that was popular from the mid-1960s to the early 1980s, when the Compact Cassette tape, which predated 8-track, surpassed it in popularity for pre-recorded music. The format is obsolete and was relatively unknown outside the United States, the United Kingdom, Canada, New Zealand, Australia, Germany, Italy, and Japan. The main advantage of the 8-track tape cartridge is that it does not have to be "flipped over" to play the alternative set of tracks.
Quadraphonic sound – equivalent to what is now called 4.0 surround sound – uses four audio channels in which speakers are positioned at the four corners of a listening space. The system allows for the reproduction of sound signals that are independent of one another.
Surround sound is a technique for enriching the fidelity and depth of sound reproduction by using multiple audio channels from speakers that surround the listener. Its first application was in movie theaters. Prior to surround sound, theater sound systems commonly had three "screen channels" of sound that played from three loudspeakers located in front of the audience. Surround sound adds one or more channels from loudspeakers to the side or behind the listener that are able to create the sensation of sound coming from any horizontal direction around the listener.
In music, tape loops are loops of magnetic tape used to create repetitive, rhythmic musical patterns or dense layers of sound when played on a tape recorder. Originating in the 1940s with the work of Pierre Schaeffer, they were used among contemporary composers of 1950s and 1960s, such as Éliane Radigue, Steve Reich, Terry Riley, and Karlheinz Stockhausen, who used them to create phase patterns, rhythms, textures, and timbres. Popular music authors of 1960s and 1970s, particularly in psychedelic, progressive and ambient genres, used tape loops to accompany their music with innovative sound effects. In the 1980s, analog audio and tape loops with it gave way to digital audio and application of computers to generate and process sound.
Electroacoustic music is a genre of Western art music in which composers use technology to manipulate the timbres of acoustic sounds, sometimes by using audio signal processing, such as reverb or harmonizing, on acoustical instruments. It originated around the middle of the 20th century, following the incorporation of electric sound production into compositional practice. The initial developments in electroacoustic music composition to fixed media during the 20th century are associated with the activities of the Groupe de recherches musicales at the ORTF in Paris, the home of musique concrète, the Studio for Electronic Music in Cologne, where the focus was on the composition of elektronische Musik, and the Columbia-Princeton Electronic Music Center in New York City, where tape music, electronic music, and computer music were all explored. Practical electronic music instruments began to appear in the early 1900s.
7.1 surround sound is the common name for an eight-channel surround audio system commonly used in home theatre configurations. It adds two additional speakers to the more conventional six-channel (5.1) audio configuration. As with 5.1 surround sound, 7.1 surround sound positional audio uses the standard front left and right, center, and LFE (subwoofer) speaker configuration. However, whereas a 5.1 surround sound system combines both surround and rear channel effects into two channels, a 7.1 surround system splits the surround and rear channel information into four distinct channels, in which sound effects are directed to left and right surround channels, plus two rear surround channels.
Lotus is a 1974 live album by the Latin rock band Santana, recorded at the Osaka Kōsei Nenkin Kaikan, Osaka, Japan in July 1973, during their Caravanserai Tour. It was originally released in 1974 as a triple vinyl LP in Japan only. This version of the album was later released internationally.
Delay is an audio signal processing technique and an effects unit which records an input signal to an audio storage medium, and then plays it back after a period of time. The delayed signal may either be played back multiple times, or played back into the recording again, to create the sound of a repeating, decaying echo.
Kontakte ("Contacts") is an electronic music work by Karlheinz Stockhausen, realized in 1958–60 at the Westdeutscher Rundfunk (WDR) electronic-music studio in Cologne with the assistance of Gottfried Michael Koenig. The score is Nr. 12 in the composer's catalogue of works, and is dedicated to Otto Tomek.
Mikrophonie is the title given by Karlheinz Stockhausen to two of his compositions, written in 1964 and 1965, in which "normally inaudible vibrations ... are made audible by an active process of sound detection ; the microphone is used actively as a musical instrument, in contrast to its former passive function of reproducing sounds as faithfully as possible".
SQ Quadraphonic was a matrix 4-channel quadraphonic sound system for vinyl LP records. It was introduced by CBS Records in 1971. Many recordings using this technology were released on LP during the 1970s.
Hymnen is an electronic and concrete work, with optional live performers, by Karlheinz Stockhausen, composed in 1966–67, and elaborated in 1969. In the composer's catalog of works, it is Nr. 22.
Telemusik is an electronic composition by Karlheinz Stockhausen, and is number 20 in his catalog of works.
In sound recording and reproduction, audio mixing is the process of optimizing and combining multitrack recordings into a final mono, stereo or surround sound product. In the process of combining the separate tracks, their relative levels are adjusted and balanced and various processes such as equalization and compression are commonly applied to individual tracks, groups of tracks, and the overall mix. In stereo and surround sound mixing, the placement of the tracks within the stereo field are adjusted and balanced. Audio mixing techniques and approaches vary widely and have a significant influence on the final product.
Home audio systems are audio electronics intended for home entertainment use, such as shelf stereos, music centres and surround sound receivers. Home audio generally does not include standard equipment such as built-in television speakers, but rather accessory equipment, which may be intended to enhance or replace standard equipment, such as standard TV speakers. Since surround sound receivers, which are primarily intended to enhance the reproduction of a movie, are the most popular home audio device, the primary field of home audio is home cinema.
Spatial music is composed music that intentionally exploits sound localization. Though present in Western music from biblical times in the form of the antiphon, as a component specific to new musical techniques the concept of spatial music was introduced as early as 1928 in Germany.
Cosmic Pulses is the last electronic composition by Karlheinz Stockhausen, and it is number 93 in his catalog of works. Its duration is 32 minutes. The piece has been described as "a sonic roller coaster", "a Copernican asylum", and a "tornado watch".
Oktophonie (Octophony) is a 1991 octophonic electronic-music composition by Karlheinz Stockhausen. A component layer of act 2 of the opera Dienstag aus Licht, it may also be performed as an independent composition. It has a duration of 69 minutes.
Williams Mix (1951–1953) is a 4'15" electronic composition by John Cage for eight simultaneously played independent quarter-inch magnetic tapes. The first octophonic music, the piece was created by Cage with the assistance of Earle Brown, Morton Feldman, and David Tudor, using many tape sound sources and a paper score he created for the construction. "Presignifying the development of algorithmic composition, granular synthesis and sound diffusion," it was the third of five pieces completed in the Project for Music for Magnetic Tape (1951–1954), funded by dedicatee architect Paul Williams.
Mixed music is music combining acoustic instruments and fixed-media electronics or more generally, music which combines acoustic-instrumental and electronic sounds sources ; mixed music is therefore a subcategory of electronic music. While this term could be applied to many genres, the term mixed music generally refers to contemporary classical music repertoire and is therefore distinct from live electronic music.