A process whereby the pitch of a selected track or part can be changed (or corrected) without changing the speed at which it occurs. A crude ability to do this has been around for some time, but only in recent years has the technology reached a level where it’s practical and easy to apply. One of the first devices to come out that made this possible was the old Eventide Harmonizer“, a device designed for generating harmony parts. By today’s standards it didn’t work all that well due to the fact that formants were also shifted in pitch, which gives you the Mickey Mouse or Darth Vader effect depending on whether you are moving the pitch up or down. And for pitch correction it was entirely a manual process that was a bit hit or miss in terms of quality. Later, devices (including more sophisticated Eventide units) and software arrived that could handle formants separately, which allowed users to create much more realistic harmony effects. Though the sound was much better actually correcting pitch problems in a track was still largely a manual process that could take hours. Over the years technology has improved to a point where software and/or hardware can now correct the pitch of a whole track (or live performance) automatically just by knowing the key and tuning of the song. And if applied sensibly there are so few side effects that listeners can’t tell the performance has been treated electronically.