ABSTRACT
This chapter explains the basics of pitch shifting and time stretching and shows how they’re implemented. Implementing Vari-Speed type pitch shifting digitally is relatively straightforward: The audio is simply played back at a faster or slower sample rate than when it was recorded. Digital signal processing pitch shifting algorithms have improved, and some newer programs and plug-ins can shift more than a few percent without audible artifacts. Auto-Tune, from the company Antares, was the first contemporary hardware device—soon followed by a plug-in version—that could automatically track and correct pitch as it changes over time. Besides correcting out-of-tune singers, independent pitch shift and time stretch are used with Acidized Wave files in audio looping programs. Acidized Wave files are used to create complete songs and backings, using loop libraries that contain short musical phrases that are strung together. Multiplying retains the musical relationship between notes and between the harmonics within a single note.
