In the past, this was only possible through faster or slower playback of (analog) sound carriers; today, digital audio workstations or special pitch shifters are available for this purpose. With acoustic musical instruments, glissando describes a sliding change in pitch .
The effect is best known in various Disney films (Chip & Chap) and with the Smurfs (the so-called Smurfs voice). The problem with this technique was and remains that the original speed is falsified and the voice is spoken too quickly, especially when pitching the voice up. In order to counteract this effect, the speakers had to speak slower or faster.
In modern audio technology, a temporal extension (so-called creates time-stretching ) Remedy. It allows the playback speed to be changed without affecting the pitch of the audio material. Today's software algorithms for changing pitch are therefore also equipped with a function for time-stretching.
A change in pitch or stretching over time can only sound 'realistic' within certain limits. Values of around 15 to 20 percent deviation from the original material produce audible noise ( grain or reverberation artifacts ) that audibly alienate the original, which is sometimes used as an effect.
Maintaining the formants is important for the lifelike sound of human voices and singing after a pitch change . These are natural resonances of the speech apparatus that are usually shifted when the pitch is changed, resulting in a strong alienation ( Mickey Mouse effect).
Automatic pitch correction
Automatic pitch correction is a special type of pitch change that is often used when recording vocals.
Pitch changes are used in music production as a sound effect to influence the sound image. For example, music and playback systems specializing in karaoke offer this function to enable inexperienced singers to easily adapt the music to the difficult-to-change pitch of the singing voice. It can also be used to adjust audio clips of different pitches and tempos if they cannot be replayed or sampled . In addition, this technology enables the playable pitch of an instrument to be extended (e.g. a guitar can be calculated an octave lower).
Feedback pitch shifters are u. a. the Harmonizer from Eventide and the Super Shifter from Boss. Through the feedback, an artificially increased tone at the output can be fed back into the input, to be increased again and so on. This creates a rapidly ascending arpeggio.
There are numerous free and commercial software packages or modules for audio processing that can change the pitch or playback speed, e.g. B .:
- Roland Enders: The home recording manual. 3rd edition, Carstensen Verlag, Munich, 2003, ISBN 3-910098-25-8
- Thomas Görne: Sound engineering. 1st edition, Carl Hanser Verlag, Leipzig, 2006, ISBN 3-446-40198-9