The business was founded in the basement of the Sound Exchange, a recording studio located at 265 West 54th Street in New York City and owned by Greene.

Other early products included a two-second delay for telephone research and an electrostatic deflector for dispensing nanoliter quantities of chemical reagents.

[2] Eventide's original product line consisted of two products: the Instant Phaser[3] (the result of an Audio Engineering Society Show appearance and Eventide's first answer to tape-based flanging), and what would become the 1745 Digital Delay Line[4] (the result of a significant order from Maryland Public Broadcasting and the world's first digital pro audio device).

These mission-critical recording systems capture, store, protect, reproduce, and manage important multimedia interactions and critical data.

The production H910 was released in 1975, offering pitch shifting (±1 octave), delay (up to 112.5 ms), feedback regeneration and other features in an easy-to-use box that sold for $1,600.

[citation needed] The first H910 customer was New York City's Channel 5, utilizing it to downward pitch shift I Love Lucy reruns that were sped up to create room to run more advertisements.

Notable users of this twin Harmonizer effect included Eddie Van Halen, who used it for his trademark guitar sound, and Tom Lord-Alge, who used it for the vocals on the hit Steve Winwood song "Back in the High Life Again" (1986).