Pitch shift

Pitch shift is a sound recording technique, in which the normal pitch or tone of a sound is altered ("shifted"), for effect or for other purposes.

Pitch-shifting may be done both in analog and in digital recording. In analog recording, the pitch is changed by raising or lowering the voltage being sent to the capstan of the tape machine, in a process often called vari-speed. (An older method used on reel-to-reel machines was a "wrap" or cover over the capstan, which changed its effective width.) In digital recording, shifting is accomplished through digital signal processing. Older digital processors could often only shift pitch in post-production; many modern devices can change pitch in real time.

Pitch may be changed in a recording for a number of reasons. The sound of an instrument or voice might be modified slightly, to make a vocalist or instrumentalist's job easier in dealing with difficult keys, and usually involves no more than a half-step (semitone) or possibly whole step (whole tone) change. Vocal pitch may also be speeded up to "smooth out" a performance, or to make the singer sound younger, as on some Chuck Berry recordings. (Berry was already in his thirties when he began having hits; his producer wanted him to appeal to the youth market.)

The audio texture of a sound may be changed substantially by changing pitch, and this effect is sometimes desirable. The famous Chipmunks recordings with David Seville (aka Ross Bagdasarian) were created by recording vocal tracks at a slow speed, then boosting them to normal at playback. (The latter-day Chipmunks cartoons were voiced using real-time digital pitch-shift; the differences in enunciation between old and new are noticeably different.) Voice artist Mel Blanc gave Tweety and Daffy Duck their voices through altered pitch (Daffy's voice essentially being Sylvester the Cat's played back faster than normal).

Jimi Hendrix added slowed-down voices to his song "Third Stone from the Sun", while Donovan used both low and high pitches to voice the characters in his adaptation of Lewis Carroll's "The Walrus and the Carpenter" for record. Record producer George Martin added flavour to pop records by recording piano tracks an octave low, then speeding them up, as with Billy J. Kramer's hit "Bad To Me". Many of the Beatles's records from 1966 and 1967 were made by recording instrumental tracks a half-step high, then the vocals correspondingly low, to alter the natural tonal qualities of each. (Examples of this include the songs "Rain", "I'm Only Sleeping" and "When I'm Sixty-Four".)

Pitch correction
Pitch correction, to fix imperfect pitch in a vocal performance, became possible with the advent of real-time digital technology. Early machines such as the Eventide Harmonizer were limited in their abilities, not to mention costly; newer methods, such as the Antares Auto-Tune, have aided countless vocals on pop music recordings, with machines and plug-ins being relatively inexpensive. Auto-Tune devices (including the Antares AVP-1 Vocal Processor) are standard equipment in contemporary recording studios.