DJ mix in the context of "Live sound mixing"

A disc jockey, more commonly abbreviated as DJ, is a person who plays recorded music for an audience. Types of DJs include radio DJs (who host programs on music radio stations), club DJs (who work at nightclubs or music festivals), mobile DJs (who are hired to work at public and private events such as weddings, parties, or festivals), and turntablists (who use record players, usually turntables, to manipulate sounds on phonograph records). Originally, the "disc" in "disc jockey" referred to shellac and later vinyl records, but nowadays DJ is used as an all-encompassing term to also describe persons who mix music from other recording media such as cassettes, CDs or digital audio files on a CDJ, controller, or even a laptop. DJs may adopt the title "DJ" in front of their real names, adopted pseudonyms, or stage names.

DJs commonly use audio equipment that can play at least two sources of recorded music simultaneously. This enables them to blend tracks together to create transitions between recordings and develop unique mixes of songs. This can involve aligning the beats of the music sources so their rhythms and tempos do not clash when played together and enable a smooth transition from one song to another. DJs often use specialized DJ mixers, small audio mixers with crossfader and cue functions to blend or transition from one song to another. Mixers are also used to pre-listen to sources of recorded music in headphones and adjust upcoming tracks to mix with currently playing music. DJ software can be used with a DJ controller device to mix audio files on a computer instead of a console mixer. DJs may also use a microphone to speak to the audience; effects units such as reverb to create sound effects and electronic musical instruments such as drum machines and synthesizers.

Electronic dance music (EDM), also referred to as dance music or club music, is a broad range of percussive electronic music genres originally made for nightclubs, raves, and festivals. It is generally produced for playback by DJs who create seamless selections of tracks, called a DJ mix, by segueing from one recording to another. EDM producers also perform their music live in a concert or festival setting in what is sometimes called a live PA. Since its inception EDM has expanded to include a wide range of subgenres.

During the late 1980s to early 1990s, following the emergence of electronic music instruments, rave culture, pirate radio, party crews, underground festivals, and an upsurge of interest in club culture, EDM achieved mainstream popularity in Europe and Japan. However, rave culture was not as broadly popular in the United States; it was not typically seen outside of the regional scenes in New York City, Florida, the Midwest, and California. Although the pioneer genres of electro, Chicago house and Detroit techno were influential both in Europe and the United States, mainstream media outlets and the record industry in the United States remained openly hostile to it until the 1990s and beyond. There was also a perceived association between EDM and drug culture, which led governments at state and city levels to enact laws and policies intended to halt the spread of rave culture.

Techno is a genre of electronic dance music (EDM) which is generally produced for use in a continuous DJ set, with tempos being in the range from 120 to 150 beats per minute (bpm). The central rhythm is typically in common time (
₄) and often characterized by a repetitive four on the floor beat. Artists may use electronic instruments such as drum machines, sequencers, and synthesizers, as well as digital audio workstations. Drum machines from the 1980s such as Roland's Roland TR-808 and Roland TR-909 are highly prized, and software emulations of such retro instruments are popular in this style.

Much of the instrumentation in techno is used to emphasize the role of rhythm over other musical aspects. Vocals and melodies are uncommon. The use of sound synthesis in developing distinctive timbres tends to feature more prominently. Typical harmonic practices found in other forms of music are often ignored in favor of repetitive sequences of notes. More generally the creation of techno is heavily dependent on music production technology.

Beatmatching or pitch cue is a DJ technique of pitch shifting or time stretching an upcoming track to match its tempo to that of the currently playing track, and to adjust them such that the beats (and, usually, the bars) are synchronized—e.g. the kicks and snares in two house records hit at the same time when both records are played simultaneously. Beatmatching is a component of beatmixing which employs beatmatching combined with equalization, attention to phrasing and track selection in an attempt to make a single mix that flows together and has a good structure.

Beatmatching is a core technique for DJing electronic dance music, and it is standard practice in clubs to keep a constant beat throughout the night, even if DJs change in the middle.