Pitch control

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 33, 45 or even 78 rpm on a turntable), resulting in adjustments in pitch.

Superscope, Inc. of Sun Valley added vari-speed as a feature of portable cassette decks in 1975.

[4][5] For DJs the possibility to alter the pitch on their turntables or CD players is standard.

By changing the pitch the DJ can alter the BPM of a record within this limited range.

This is a key component for beatmatching, enabling the DJ to get two records to play at the same BPM thereby synchronising the beat for the dancers.