A disc jockey (abbreviated D.J. or DJ) is a person who plays recorded music for an audience. Originally, "disc" (sometimes spelled "disk", although this is now uncommon) referred to phonograph records, not the later compact discs. Today, the term includes all forms of music playback, no matter the medium.

There are several types of disc jockeys. Radio DJs or radio personalities introduce and play music that is broadcast on AM, FM, shortwave, digital or internet radio stations. Club DJs select and play music in bars, nightclubs or discothèques, or at parties or raves, or even in stadiums. Hip hop DJs select and play music using multiple turntables to back up one or more MCs/rappers, perform turntable scratching to create percussive sounds, and are also often music producers who use turntablism and sampling to create backing instrumentals for new tracks. In reggae, the DJ (deejay) is a vocalist who raps, "toasts", or chats over pre-recorded rhythm tracks while the individual choosing and playing them is referred to as a selector.[1] Mobile DJs travel with portable sound systems and play recorded music at a variety of events. Some mobile DJs also serve as the master of ceremonies or MC directing the attention of attendees, and maintaining a room-wide focus on what is included in the event's agenda.[2] According to a 2012 study, there are approximately 1¼ million professional disc jockeys in the world.[3]

The title "DJ" is also commonly used by DJs in front of their real names or adopted pseudonyms as a title to denote their profession and the music they play

Hardtechno refers to a style of Techno, which evolved after 2000 from Schranz and Hardcore Techno. While the first harder Techno productions appeared around 1991 on labels such as PCP and Industrial Strength, these were referred to as Hardcore Techno. Over the years, the Hardcore scene cultivated a new sound far away from its Techno origins, whereas Techno itself went in a softer direction.

At the end of the 1990s, fueled by the Schranz movement, a new, extremely hard style of Techno became popular, which is now generally referred to as Hardtechno. This style runs at very high bpm, usually 150 or more and features heavy distortion and prominent kickdrums. By 2007, almost all major European Techno festivals, such as I Love Techno, Awakenings, MayDay, Nature One, Mystery Land featured a Hardtechno stage or at least one Hardtechno artist. It has also been the main focus of festivals like "Hardtechno Festival" in Vienna (attendance 2,000+) or Syndicate in Dortmund (attendance 10,000).

House music é um estilo musical surgido em Chicago, nos Estados Unidos, na primeira metade da década de 1980. A origem do nome se deu devido a esse novo estilo de dance music que surgia e começava a ser tocada na casa noturna chamada Warehouse. Os frequentadores da casa iam às lojas de discos a procura das músicas que ouviam no club e pediam por "aquela música da Warehouse", até as lojas começarem a encurtar o nome de Warehouse Music, para apenas house. Muitos dizem que a house music é uma vertente da disco music e da electropop dos anos 70, pois foram estilos de música quase que contemporâneos1 . Frankie Knuckles é aclamado por muitos como o "pai" da House Music2 , ele que é um dos pioneiros deste gênero juntamente com outros nomes como Tony Humphries3 . Atualmente existem muitas sub-vertentes do house, tais como: funky-house, tech-house, disco-house, progressive house, electro-house, acid house, soulful house, neo-jazz-house, entre outros.4

O elemento comum de quase toda a house music é uma batida 4/4 gerada numa bateria eletrônica, completada com uma sólida (muitas vezes também gerada eletronicamente) linha de baixo e, em muitos casos, acréscimos de "samplers", ou pequenas porções de voz ou de instrumentos de outras músicas. Representa, de certa forma, também uma evolução da disco music dos anos 70. A maioria dos projetos (desenvolvidos por DJs e produtores) e grupos de house music têm como origem a Itália, a Alemanha, a Bélgica, além dos Estados Unidos e Reino Unido.

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