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.23
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 1995.45
Pitch control is fundamental for DJing. By changing pitch, a DJ can alter the speed of an upcoming track to match its tempo to that of the currently playing track so that the beats are synchronized, a technique called beatmatching. Through beatmatching, a DJ can create smooth transitions between tracks in a DJ set.
Turntables, CDJs, DJ controllers, and DJ software allow DJs to change the speed at which a track is played for this purpose. Technics SL-1200 turntables allow pitch changes to +/− 8% or 16%, depending on the model, and modern DJ gear often allows a range of +/- 100% (from pausing the track to playing the track twice as fast).
Modern DJ equipment also features time stretching, which allows the speed of a track to be changed without affecting its pitch, a feature often called "Master Tempo" or "Key Lock". Some equipment also features pitch shifting, allowing pitch to be adjusted independently of tempo; this allows changing the musical key of tracks so that transitions between them sound more pleasing to the listener, a practice called harmonic mixing.
On Technics SL-1200 turntables, pressing the Reset button returns the pitch to a fixed preset value of +/−0% regardless of the pitch control position.67
"Technics SL-1210MK7R Direct Drive Turntable System Instruction Manual". 18 April 2022. https://manuals.plus/technics/sl-1210mk7r-direct-drive-turntable-system-manual#pitch_control_fine_adjustment_to_pitch ↩
Ferric-oxide Archeology,6. Superscopes and varispeed http://www.rainerlinz.net/NMA/articles/Ferric-oxide.html ↩
Marantz Far East In Name Change; Adds Superscope, Billboard Magazine, December 7, 1974, Page 40 ↩
Vari-Speed trademark 73025543 http://www.mytrademarkia.com/varispeed-73025543.html ↩
Musical Instruments & Musical Recorder https://ourvinylweighsaton.com ↩
"SL-1200 ‒ Heritage - Technics". https://www.technics.com/global/home/sl1200/heritage.html ↩