Pitch shift

For the British electronic metal band, see Pitchshifter.

POG octave effect

Pitch shifting is a sound recording technique in which the original pitch of a sound is raised or lowered. Effects units that raise or lower pitch by a pre-designated musical interval are called "pitch shifters" or "pitch benders".

Pitch/time shifting

The simplest methods are used to increase pitch and reduce note durations, or vice versa, reduce pitch and increase note duration. This can be done by replaying a sound waveform at a different speed than it was recorded. It can be accomplished by changing the diameter of the capstan drive shaft, or using a different more; on a reel-to-reel tape recorder, often by covering it with layers of suitable material, or on earlier wire recorders which have basically the same principle. Altering the capstan diameter affects the speed at which the tape registers sound, which in turn alters pitch. As technologies improved later designs of motor speeds could be controlled by electronic servo system circuits. This arrangement using “vari-speed” capstan motors allowed the speed change to be achieved more simply. As for vinyl records, the same thing can be done; placing a finger on the turnable to give friction will retard it, while giving it a 'spin' can advance it. However altering pitch and time independently is much more difficult.

Pitch shifter and harmonizer

A pitch shifter is a sound effects unit that raises or lowers the pitch of an audio signal by a preset interval. For example, a pitch shifter set to increase the pitch by a fourth will raise each note three diatonic intervals above the notes actually played. Simple pitch shifters raise or lower the pitch by one or two octaves, while more sophisticated devices offer a range of interval alterations. Pitch shifters are included in most audio processors today.

A harmonizer is a type of pitch shifter that combines the "shifted" pitch with the original pitch to create a two or more note harmony.

In digital recording, pitch shifting is accomplished through digital signal processing. Older digital processors could often only shift pitch in post-production, whereas many modern devices using computer processing technology can change pitch values in real time.

Pitch shifting should not be confused with pitch correction, a process that uses digital signal processing (DSP) software such as "Auto-Tune" to correct intonation inaccuracies in a recording or performance. Pitch shifting raises or lowers each pitch in a recording by the same diatonic interval, whereas pitch correction makes different changes from note to note.

Notable uses

Numerous cartoons have used pitch shifters to produce distinctive animal voices. The Chipmunks recordings with David Seville (aka Ross Bagdasarian) were created by recording vocal tracks at a slow speed, then playing them back at normal speeds. Voice artist Mel Blanc used pitch shifting techniques to create the voices of Tweety and Daffy Duck.

One notable early practitioner of pitch shifting in music is Chuck Berry, who used the technique to make his voice sound younger. Many of the Beatles' records from 1966 and 1967 were made by recording instrumental tracks a half-step higher and the vocals correspondingly low. Examples include "Rain", "I'm Only Sleeping", and "When I'm Sixty-Four".

The metal genre grindcore commonly uses pitch shifters to lower the pitch of the vocals, especially the goregrind sub-genre.

See also

• Effects unit
• Audio timescale-pitch modification
• Pitch control
• Timestretching
• Short-time Fourier transform
• DigiTech Whammy

External links

• Pitch shifting explained
• 4 Band Pitchshifter Open Source VST Pitch shifter based on Stephan M. Bernsee article.
• Time Stretching And Pitch Shifting of Audio Signals by Stephan M. Bernsee
• pitchsift.js from KievII Pitch shifter algorithm in Javascript, from KievII library