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Technics SL-1210MK2 turntable pitch control slider
A variable speed pitch control (or vari-speed) is a control on an audio device such as a turntable, tape recorder, or CD player that allows the operator to deviate from a standard speed (such as 33⅓, 45 or even 78 rpm on a turntable). The latter term "vari-speed" is more commonly used for tape decks, particularly in the UK. Analog pitch controls vary the voltage being used by the playback device; digital controls use digital signal processing to change the playback speed or pitch. A typical DJ deck allows the pitch to be increased or reduced by up to 8%, which is achieved by increasing or reducing the speed at which the platter rotates.
Turntable or CD playing speed may be changed for beatmatching and other DJ techniques, while pitch shift using a pitch control has myriad uses in sound recording.
Vari-Speed In Consumer Cassette Decks 
Superscope, Inc. of Sun Valley added vari-speed as a feature of portable cassette decks in 1975. The C-104 and C-105 models incorporated this feature.
Superscope trademarked the name Vari-Speed in 1974. The trademark category was Computer & Software Products & Electrical & Scientific Products. The trademark goods and Services use was Magnetic tape recorders and reproducers. The trademark expired in 1995.
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