The Eventide H910 Harmonizer was developed by Eventide in 1974. The H910 was the world’s first commercially available digital audio effects device. It combined ‘de-glitched’ pitch change with delay and feedback. It could be controlled by a keyboard remote control to instantly shift pitch in half steps. It featured a two octave range and up to 112.5 msec of delay. The combination of pitch change, delay and feedback opened up a new world of sonic possibilities which were exploited in the ground-breaking work by artists from AC/DC to David Bowie to Frank Zappa.
The H910 was used to create the effects heard on records since the late seventies.