A disc jockey, often abbreviated as DJ, is a person who plays existing recorded music for a live audience. Most common types of DJs include radio DJ, club DJ who performs at a nightclub or music festival, and turntablist who uses record players, usually turntables, to manipulate sounds on phonograph records. Originally, the "disc" in "disc jockey" referred to gramophone records, but now "DJ" is used as an all-encompassing term to describe someone who mixes recorded music from any source, including cassettes, CDs, or digital audio files on a CDJ or laptop. The title "DJ" is commonly used by DJs in front of their real names or adopted pseudonyms or stage names.

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 advanced music-mixing procedures than club DJs, who rely on a smooth transition between songs using a range of techniques. However, some radio DJs are experienced club DJs, so they use the same sophisticated mixing techniques.  Club DJ turntable techniques include beatmatching, phrasing and slip-cueing to preserve energy on a dance floor. 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 (although 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.  Recent advances in technology in both DJ hardware and software can provide assisted or automatic completion of some traditional DJ techniques and skills. Examples include phrasing and beatmatching, which can be partially or completely automated by utilizing DJ software that performs automatic synchronization of sound recordings, a feature commonly labelled "sync". Most DJ mixers now include a beat-counter which analyzes the tempo of an incoming sound source and displays its tempo in beats per minute (BPM), which may assist with beatmatching analog sound sources.  In the past, being a DJ has largely been a self-taught craft but with the complexities of new technologies and the convergence with music production methods, there are a growing number of schools and organizations that offer instruction on the techniques.

What is one technique used by disc jockeys?
These techniques primarily include the cueing, equalization and audio mixing of two or more sound sources.