A DJ mix or DJ mixset is a sequence of musical tracks typically mixed together to appear as one continuous track. DJ mixes are usually performed using a DJ mixer and multiple sounds sources, such as turntables, CD players, digital audio players or computer sound cards, sometimes with the addition of samplers and effects units, although it is possible to create one using sound editing software. DJ mixing is significantly different from live sound mixing. Remix services were offered beginning in the late 1970s in order to provide music which was more easily beatmixed by DJs for the dancefloor. One of the earliest DJs to refine their mixing skills was DJ Kool Herc. Francis Grasso was the first DJ to use headphones and a basic form of mixing at the New York City nightclub Sanctuary. Upon its release in 2000, Paul Oakenfold's Perfecto Presents: Another World became the biggest selling DJ mix album in the US. Music A DJ mixes music from genres that fit into the more general term electronic dance music. Other genres mixed by DJ includes hip hop, breakbeat and disco. Four on the floor disco beats can be used to create seamless mixes so as to keep dancers locked to the dancefloor. Two main characteristics of music used in DJ mixes is a dominant bassline and repetitive beats. Music mixed by DJs usually has a tempo which ranges from 100 bpm up to 160 bpm. Technique A DJ mixset is usually performed live in front of an audience in a nightclub, party, or rave setting. Mixsets can also be performed live on radio or recorded in a studio. Methods of mixing vary slightly depending on the music genres being played. House and trance DJs tend to aim for smooth, blended mixes while hip-hop DJs may use turntablism, scratching and other cutting techniques. Some DJs, particularly those mixing Goa trance may prefer to mix during a break in which instead of beats, washes of synthesized sounds are combined. Further refinement to the mixing quality can be provided with harmonic mixing which avoids dissonant tones during a mix. In live situations, the progression of the DJ set is a dynamic process. The DJ chooses tracks partly in response to the activity on the dance floor. If the dance floor becomes less active, the DJ will make a judgement as to what track will increase dance floor activity. This