What is it?
The H910 (2U rack unit) was the first studio harmonizer produced by Eventide; designed by Tony Agnello it was first demonstrated at the 1974 AES show and released in 1975. The unit number '910' is inspired by the Beatles "One After 909" - the sound became familiar on many recordings of the time: Jon Anderson (prototype tester), Frank Zappa, Bowie, AC/DC, the Cars, Van Halen, Tom Lord-Algae, Steve Winwood, and many many more.
What does it do?
The H910 can process an audio signal adding pitch-shift (+/- one octave) and delay (up to 112.5ms).
The sound of the unit can be described as adding a shimmer to the audio signal rather like a chorus on guitar or vocals; at a slight pitch-shift the effect is harmonious and adds a nice 'doubling' quality which thickens source signals...at more extreme settings the sound becomes weird, robotic and glitchy in a lo-fi way and the weirdness can be extended into soundscape FX by manipulating the pitch and anti-feedback dials and delay buttons in realtime. It works great on many sources: vocals, guitar, bass, keys, drums, samples...even as a mix effect.
How does it work?
A rotary dial controls input level and a related push-button selects for mic (?) or line level. There's an LED to signal when limiting on the input is operating. The pitch and delay can be adjusted via rotary dials - a third dial adjusts 'anti-feedback' which decreases the resonance of the delayed signal. A series of white push buttons control: delay time (+ all buttons in 1176-style) for each output. Input is via binding posts and there are two separate outputs on binding posts, each having a variable delay. There's also an optional keyboard with which the pitch can be played in realtime. The H910 is quite unpredictable and it's often a chaotic alchemical experiment to get a workable sound and it's hard to repeat the settings...but I quite like that.
The unit is great fun to operate being somewhat intuitive to use: turning up the feedback can result in huge sounding sweeps and it possible to get melodic and chirpy artifacts that are unique to the H910's processing. I enjoyed what a simple detune did to electro-acoustic guitar giving it a Bowie-esque vibe (that 70's studio hi-fi sound)...nice too on vocals especially for early Human League/Depeche Mode style vibe...I guess these units were quite common in studios in that period.
This is a classic-sounding unit but it's more too...it's a piece of outboard history and the H910 is a component of the sound on many popular recordings - particularly the mid-to-late 70's/early 80's. I can emulate the sounds it produces ITB or using a Lexicon MPX110 but it's not quite the same and this is born out by Eventide's inclusion of the H910 algorithm in the Pitchfactor Stomp Box. The sound quality isn't 'perfect' but it's perfect at what it does, the features (for the time...mid 70's) are a major technological feat.