A disc jockey (also known as DJ or deejay) is a person who selects and plays recorded music for an audience.
There are several types of disc jockeys. Radio DJs introduce and play music that is broadcast on AM, FM, shortwave, digital or online radio stations. Club DJs select and play music in a bar, club, disco, a rave, or even a stadium. Hip hop disc jockeys select, play and create music with multiple turntables, often to back up one or more MCs. In reggae, the disc jockey (deejay) is a vocalist who raps, toasts or chats over recorded rhythm tracks while the individual choosing and playing them is referred to as a selector. Mobile disc jockeys travel with portable sound systems and play at a variety of events.
 Equipment and techniques
DJ equipment may consist of:
- Sound recordings in a DJs preferred medium (eg. vinyl records, compact discs, computer media files)
- A combination of two devices, or sometimes one if playback is digital, to play sound recordings, for alternating back and forth to create a continuous playback of music (e.g. record players, compact disc players, computer media players such as an MP3 player)
- A sound system for amplification or broadcasting of the recordings (e.g. portable audio system, PA system) or a radio broadcasting system.
- A DJ mixer, an electronic, usually two-four channel, mixer with a crossfader used to smoothly go from one song to another (using two or more playback devices)
- Headphones, used to listen to one recording while the other recording is being played to the audience, and
- Optionally, a microphone, so that the DJ can introduce songs and speak to the audience.
Other equipment could or can be added to the basic DJ set-up (above) providing unique sound manipulations. Such devices include, but are not limited to:
- Electronic effects units (delay, reverb, octave, equalizer, chorus, etc). Some club DJs use a suboctave effect which creates a very low bass sound and adds it to the mix.
- A computerised performance system, which can be used with timecode encoded vinyl/CD content to manipulate digital files on the computer in real time.
- Multi-stylus headshells, which allow a DJ to play different grooves of the same record at the same time.
- Special DJ digital controller hardware can manipulate digital files on a PC or laptop, by using midi signals
- Samplers, sequencers, electronic musical keyboards (synthesizers), or drum machines.
Several techniques are used by DJs as a means to better mix and blend recorded music. These techniques primarily include the cueing, equalization and audio mixing of two or more sound sources. The complexity and frequency of special techniques depends largely on the setting in which a DJ is working. Radio DJs are less likely to focus on music-mixing technique than club DJs, who rely on a smooth transition between songs using a range of techniques.
Club DJ turntable techniques include beatmatching, phrasing, and slip-cueing to preserve energy on a dancefloor. Turntablism embodies the art of cutting, beat juggling, scratching, needle drops, phase shifting, back spinning, and more to perform the transitions and overdubs of samples in a more creative manner (though turntablism is often considered a use of the turntable as a musical instrument, rather than a tool for blending recorded music). Professional DJs may use harmonic mixing to choose songs that are in compatible musical keys.
The role of selecting and playing recorded music for an intended audience is the same for every disc jockey. The selected music, the audience, the setting, the preferred medium, and the level of sophistication of sound manipulation are factors that differentiate different DJ types.
 Radio disc jockeys
Famous American radio disc jockeys such as Alan Freed, Scott Muni, Casey Kasem, Dick Biondi, Wolfman Jack and Dr. Demento built their audiences using a combination of the nature of the songs they selected and a strong on-air personality. Modern-day commercial radio disc jockeys typically rely on their on-air character alone as the station's playlist has been predetermined by a program director or music director.
Radio disc jockeys appear in a wide range of broadcast formats, from Top 40 or Contemporary Hit Radio to Oldies and other formats that are defined by the type of songs played. Other formats are defined by the type of originating station, with public radio, college radio and pirate radio as examples. Some national governments operate official radio stations for a global audience, such as Voice of America hosted by the United States and Voice of Russia organized by the Russian government. These stations may include programs by disc jockeys; The Clash frontman Joe Strummer played selections from his musical library for the UK's BBC World Service in the 1990s. Large military units sometimes broadcast their own radio programs to their troops, inserting news, weather reports and advice between popular songs. The film Good Morning, Vietnam portrays an American military disc jockey.
 Reggae deejays
In reggae music (specifically dancehall), the deejay is traditionally a vocalist who raps, toasts or chats to a "riddim". The term "selector" is reserved for the person who just selects the record and plays it over the sound system.
 Club disc jockeys
Using several turntables, CD players or a hard drive source, a club disc jockey selects and plays music in a club setting. The setting can range anywhere from a neighborhood party or a small club to a disco, a rave, or even a stadium. The main focus of club DJs is on the music they play and how they remix tracks in and out of each other or also just to add a bit of energy to a track. They build their sets by choosing tracks to control the energy level of the crowd and use beatmixing (or "beatmatching") technique for seamless transition between tracks. For more information, see Notable Club DJs.
 Hip hop disc jockeys
- See also: Turntablism
 Mobile disc jockeys
Mobile Disc Jockeys are an extension of the original Radio disc jockeys. They travel with or go on tour with mobile sound systems and play from an extensive collection of recorded content for a specific audience. In the 2000s, mobile DJs need a large selection of music, professional-grade equipment, good organizational skills, vocal talent as an MC, mixing skills, quality lighting, insurance for liability, and on-site back-up equipment. In the 2000s, the role of the Mobile DJ has expanded. Many Mobile DJs have assumed additional responsibilities to ensure an event's success. These responsibilities include the roles of MC, event organizer and coordinator, lighting director, and/or sound engineer.
In the past, Mobile DJs utilized vinyl records or cassettes. During the Disco era of the 1970s, demand for Mobile DJs (called Mobile Discos in the UK) soared, and top Disc Jockeys travelled with hundreds of vinyl records and cassette tapes. In the 1990s, Compact Disc became the standard. Mobile Disc Jockey trade publications such as DJ Times magazine and Mobile Beat were founded in this era.Mobile DJs have formed professional associations such as the Canadian Disc Jockey Association (CDJA), the Canadian Online Disc Jockey Association (CODJA), the American Disc Jockey Association (ADJA), and the National Association of Mobile Entertainers In the UK, associations include the National Association of Disc Jockeys (NADJ), and the South Eastern Discotheque Association (SEDA).
Today, many Mobile DJs rely heavily on laptop computers and MP3s for sequencing and mixing.  This technology allows DJs to do mixing prior to an event as well as lightens the load by reducing the number of CDs that a DJ must carry.
 Mid-1800s to 1920s
In 1857, Leon Scott invented the phonoautograph in France, the first device to record sound. In 1877, Charles Cros invented the phonograph in France (it was patented before Edison's invention but never built) and Thomas Alva Edison invented the phonograph cylinder, the first device to play back recorded sound, in the United States. In 1892, Emile Berliner began commercial production of his gramophone records, the first disc record to be offered to the public. In 1906, Reginald Fessenden transmitted the first audio radio broadcast in history also playing the first record, a contralto singing Handel's Largo from Xerxes.
The world's first radio disc jockey was Ray Newby of Stockton California. In 1909, at 16 years of age, Newby began regularly playing records on a small spark transmitter while a student at Herrold College of Engineering and Wireless located in San Jose, California, under the authority of radio pioneer, Charles "Doc" Herrold.
We used popular records at that time, mainly caruso records because they were very good and loud; we needed a boost... we started on an experimental basis and then because this is novel, we stayed on schedule continually without leaving the air at any time from that time on except for a very short time during World War I when the government required us to remove the antenna... Most of our programming was records, I'll admit, but of course we gave out news as we could obtain it...—Ray Newby, I've Got a Secret (1965)
By 1910 regular radio broadcasting had started to use "live" as well as pre-recorded sound. In the early radio age, content typically included comedy, drama, news, music, and sports reporting. The on-air announcers and programmers would later be known as disc jockeys. In the 1920s - juke joints became popular as places for dancing and drinking to recorded jukebox music. In 1927, Christopher Stone became the first radio announcer and programmer in the United Kingdom, on the BBC radio station. In 1929, Thomas Edison ceased phonograph cylinder manufacture, ending the disc and cylinder rivalry.
In 1935, American commentator Walter Winchell coined the term "disc jockey" (the combination of "disc", referring to the disc records, and "jockey", which is an operator of a machine) as a description of radio announcer Martin Block, the first announcer to become a star. While his audience was awaiting developments in the Lindbergh kidnapping, Block played records and created the illusion that he was broadcasting from a ballroom, with the nation’s top dance bands performing live. The show, which he called Make Believe Ballroom, was an instant hit. The term "disc jockey" appeared in print in Variety in 1941.
In 1943, Jimmy Savile launched the world's first DJ dance party by playing jazz records in the upstairs function room of the Loyal Order of Ancient Shepherd's in Otley, England. In 1947, he became the first DJ to use twin turntables for continuous play. In 1947, the Whiskey à Go-Go nightclub opened in Paris, France, considered to be the world's first discothèque, or disco (deriving its name from the French word, meaning a nightclub where the featured entertainment is recorded music rather than an on-stage band). Discos began appearing across Europe and the United States. From the late 1940s to early 1950s, the introduction of television eroded the popularity of radio's early format, causing it to take on the general form it has today, with a strong focus on music, news and sports.
In the 1950s, American radio DJs would appear live at "sock hops" and "platter parties" and assume the role of a human jukebox. They would usually play 45-rpm records featuring hit singles on one turntable, while talking between songs. In some cases, a live drummer was hired to play beats between songs to maintain the dance floor. In 1955 Bob Casey, a well-known "sock hop" DJ, introduced the first two-turntable system for alternating back and forth between records, creating a continuous playback of music. Throughout the 1950s, payola payments by record companies to DJs in return for airplay were an ongoing problem. Part of the fallout from the payola scandal was tighter control of the music by station management. The Top 40 format emerged, where popular songs are played repeatedly.
In the late 1950s, sound systems, a new form of public entertainment, are developed in the ghettos of Kingston, Jamaica. Promoters, who called themselves DJs, would throw large parties in the streets that centered on the disc jockey, called the "selector," who played dance music from large, loud PA systems and bantered over the music with a boastful, rhythmic chanting style called "toasting." These parties quickly became profitable for the promoters, who would sell admission, food and alcohol, leading to fierce competition between DJs for the biggest sound systems and newest records.
 1960s and 1970s
In the mid-1960s, nightclubs and discotheques continued to grow in Europe and the United States. Specialized DJ equipment such as Rudy Bozak's classic CMA-10-2DL mixer began to appear on the market. In 1969, American club DJ Francis Grasso popularized beatmatching at New York's Sanctuary nightclub. Beatmatching is the technique of creating seamless transitions between back-to-back records with matching beats, or tempos. Grasso also developed slip-cueing, the technique of holding a record still while the turntable is revolving underneath, releasing it at the desired moment to create a sudden transition from the previous record.
By 1968, the number of dance clubs started to decline; most American clubs either closed or were transformed into clubs featuring live bands. Neighborhood block parties that were modelled after Jamaican sound systems gained popularity in Europe and in the boroughs of New York City.
During the early 1970s, the economic downturn led most of the dance clubs to become underground gay discos. In 1973, Jamaican-born DJ Kool Herc, widely regarded as the "godfather of hip hop culture", performed at block parties in his Bronx neighborhood and developed a technique of mixing back and forth between two identical records to extend the rhythmic instrumental segment, or break. Turntablism, the art of using turntables not only to play music, but to manipulate sound and create original music, began to develop.
In 1974, Technics released the first SL-1200 turntable, which evolved into the SL-1200 MK2 in 1979, which as of the mid-2000s remains the industry standard for deejaying. In 1974, German electronic music band Kraftwerk released the 22-minute song "Autobahn", which takes up the entire first side of that LP. Years later, Kraftwerk would become a significant influence on hip hop artists such as Afrika Bambaataa and house music pioneer Frankie Knuckles. During the mid 1970s, Hip hop music and culture began to emerge, originating among urban African Americans and Latinos in New York City. The four main elements of hip hop culture were MCing (rapping), DJing, graffiti, and breakdancing.
In the mid-1970s, the soul-funk blend of dance pop known as Disco took off in the mainstream pop charts in the United States and Europe, causing discotheques to experience a rebirth. Unlike many late 1960s, clubs, which featured live bands, discotheques used the DJs selection and mixing of records as the entertainment. In 1975, Record pools began, enabling disc jockeys access to newer music from the industry in an efficient method.
In 1976, American DJ, editor, and producer Walter Gibbons remixed "Ten Percent" by Double Exposure, one of the earliest commercially released 12" singles (aka "maxi-single"). In 1977, Hip hop DJ Grand Wizard Theodore invented the scratching technique by accident. In 1979, the Sugar Hill Gang released "Rapper's Delight", the first hip hop record to become a hit. It was also the first real breakthrough for sampling, as the bassline of Chic's "Good Times" laid the foundation for the song.
In 1977, Saratoga Springs, NY disc jockey Tom L. Lewis introduced the Disco Bible (later renamed Disco Beats) which published hit disco songs listed by the beats-per-minute (the tempo), as well as by either artist or song title. Billboard ran an article on the new publication and it went national relatively quickly. The list made it easier for beginner DJs to learn how they could create seamless transitions between songs without dancers having to change their rhythm on the dance floor.
In 1981, the cable television network MTV was launched, originally devoted to music videos, especially popular rock music. The term "video jockey", or VJ, was used to describe the fresh faced youth who introduced the music videos. In 1982, the demise of disco in the mainstream by the summer of 1982 forced many nightclubs to either close or to change entertainment styles, such as by providing MTV style video dancing or live bands. Released in 1982, the song "Planet Rock" by DJ Afrika Bambaataa was the first hip-hop song to feature synthesizers. The song melded electronic hip hop beats with the melody from Kraftwerk's "Trans-Europe Express". In 1982, the compact disc reached the public market in Asia and early the following year in other markets. This event is often seen as the "Big Bang" of the digital audio revolution.
In the early 1980s, NYC disco DJ Larry Levan, known for his eclectic mixes, gained a cult following; and the Paradise Garage, the nightclub at which he spun, became the prototype for the modern dance club where the music and the DJ were showcased. Around the same time, the disco-influenced electronic style of dance music called House music emerged in Chicago. The name was derived from the Warehouse club in Chicago, where the resident DJ, Frankie Knuckles, mixed old disco classics and Eurosynth pop. House music is essentially disco music with electronic drum machine beats. The common element of most house music is a 4/4 beat generated by a drum machine or other electronic means (such as a sampler), together with a solid (usually also electronically generated) synth bassline. In 1983, Jesse Saunders released what some consider the first house music track, "On & On". The mid-1980s also saw the emergence of New York Garage, a house music hybrid that was inspired by Levan's style and sometimes eschewed the accentuated high-hats of the Chicago house sound.
During the mid-1980s, Techno music emerged from the Detroit club scene. Being geographically located between Chicago and New York, Detroit techno artists combined elements of Chicago house and New York garage along with European imports. Techno distanced itself from disco's roots by becoming almost purely electronic with synthesized beats. In 1985, the Winter Music Conference started in Fort Lauderdale Florida and becomes the premier electronic music conference for dance music disc jockeys.
In 1985, TRAX Dance Music Guide was launched by American Record Pool in Beverly Hills. It was the first national DJ-published music magazine, created on the Macintosh computer using extensive music market research and early desktop publishing tools. In 1986, "Walk This Way", a rap-rock collaboration by Run DMC and Aerosmith, became the first hip-hop song to reach the Top 10 on the Billboard Hot 100. This song was the first exposure of hip hop music, as well as the concept of the disc jockey as band member and artist, to many mainstream audiences. In 1988, DJ Times magazine was first published. It was the first US-based magazine specifically geared toward the professional mobile and club DJ.
Starting in the mid 1980s, the wedding and banquet business changed dramatically with the introduction of DJ music, replacing the bands that had been the norm. Band Leaders like Jerry Perell and others, started DJ companies, like NY Rhythm DJ Entertainers. Using their knowledge of audience participation, MC charisma and "crowd pleasing" repertory selection, the wedding music industry became almost all DJ, while combining the class and elegance of the traditional band presentation. New DJs as well as Band Leaders with years of experience and professionalism transformed the entire industry. Now everyone loves a good banquet DJ. The latest trend is to combine real musicians with the DJ music for a more personal and artistic approach.
During the early 1990s, the rave scene built on the acid house scene. Some DJs, wanting to be the only source for hearing certain tunes, used "white labels" — records with no info printed on them — in an effort to prevent other trainspotters from learning what they were spinning. The rave scene changed dance music, the image of DJs, and the nature of promoting. The innovative marketing surrounding the rave scene created the first superstar DJs who established marketable "brands" around their names and sound. Some of these celebrity DJs toured around the world and were able to branch out into other music-related activities.
During the early 1990s, the compact disc surpassed the gramophone record in popularity, but gramophone records continued to be made (although in very limited quantities) into the 21st century — particularly for club DJs and for local acts recording on small regional labels. During the mid-1990s, trance music, having run rampant in the German underground for several years, emerged as a major force in dance music throughout Europe and the UK. It became one of the world's most dominant forms dance music by the end of the 1990s, thanks to a trend away from its repetitive, hypnotic roots, and towards commercialized song structure.
In 1991, Mobile Beat magazine, geared specifically toward mobile DJs, began publishing. In 1992, MPEG which stands for the Moving Picture Experts Group, released The MPEG-1 standard, designed to produce reasonable sound at low bit rates. The lossy compression scheme MPEG-1 Layer-3, popularly known as MP3, later revolutionized the digital music domain. In 1993, the first Internet "radio station", Internet Talk Radio, was developed by Carl Malamud. Because the audio was relayed over the Internet, it was possible to access internet radio stations from anywhere in the world. This made it a popular service for both amateur and professional disc jockeys operating from a personal computer.
In 1995, the first full-time, Internet-only radio station, Radio HK, began broadcasting the music of independent bands. In 1996, Mobile Beat had its first national mobile DJ convention in Las Vegas. During the late 1990s, nu metal bands, such as Korn, Limp Bizkit, and Linkin Park, reached the height of their popularity. This new subgenre of alternative rock bore some influence from hip-hop because rhythmic innovation and syncopation are primary, often featuring DJs as band members. As well, during the late 1990s, various DJ and VJ software programs were developed, allowing personal computer users to deejay or veejay using his or her personal music or video files.
In 1998, the first MP3 digital audio player was released, the Eiger Labs MPMan F10. Final Scratch debuted at the BE Developer Conference, marking the first digital DJ system to allow DJs control of MP3 files through special time coded vinyl records or CDs. While it would take sometime for this novel concept to catch on with the "die hard Vinyl DJs", This would soon become the first step in the new Digital DJ revolution. Manufacturers joined with computer DJing pioneers to offer professional endorsements, the first being Professor Jam, who went on to develop the industry's first dedicated computer DJ convention and learning program, the "CPS (Computerized Performance System) DJ Summit", to help spread the word about the advantages of this emerging technology. In 1999, Shawn Fanning released Napster, the first of the massively popular peer-to-peer file sharing systems. During this period, the AVLA (Audio Video Licensing Agency) of Canada announced an MP3 DJing license, administered by the Canadian Recording Industry Association. This meant that DJs could apply for a license giving them the right to "burn" their own compilation CDs of "usable tracks", instead of having to cart their whole CD collections around to their gigs.
By the 2000s, new technologies such as voice tracking, allowed single DJs to send announcements across many stations. Commercial radio DJs were increasingly limited in their freedom to select which songs to play. Some music aficionados sought freeform stations that put the DJs back in control, or chose instead to listen to satellite radio services or portable music players. College radio stations and other public radio outlets continued to be the most common places for freeform play lists in the U.S.
In 2001, Apple Computer's iPod was introduced and quickly became the highest selling brand of portable digital mp3 audio player. The convenience and popularity of the iPod spawned a new type of DJ, the "MP3J". First appearing in certain East London clubs, and spreading to other music scenes, including New York City, this new DJ scene allowed the average music fan to bring two iPods to an "iPod Night", plug in to the mixer, and program a play list without the skill and equipment demanded by a more traditional DJ setup, and without needing to bring a heavy case of CDs.
In 2004 Rane introduced its own version of the digital vinyl DJ system Serato Scratch Live making improvements in overall system stability and more closely emulating the feel of true vinyl. They brought out a hardware mixer version in 2006. Soon after many nightclub deejays that had remained true vinyl record aficionados began the transition to becoming digital vinyl users. In 2006, the concept of DJ had its 100 year anniversary.