Early pitch shifting: The Eventide H910 Harmonizer

In 1975, Eventide came out with their first Harmonizer, the H910:

Designed by Anthony Agnello (later of Princeton Digital), this was a digital variant of the rotary tape head pitch shifters that I discussed earlier. Like the Lexicon Varispeech that preceded it, the H910 would be what I would label a 2-tap pitch shifter, in that there were 2 pitch shifted signals, with crossfading between the 2 signals. The H910 appears to use a fairly simple triangle wave crossfading, which means that the 2 different delayed signals will be present to a greater or lesser extent in the output at virtually all times.

So, why did the H910 become identified with pitch shifting, and the term “Harmonizer” become almost as generic as “Xerox” (at least in recording circles), while the Lexicon Varispeech faded into relative obscurity? I don’t know. If I had to guess, it has something to do with marketing. The Varispeech was described in the literature as a way of time correcting speech, while the Harmonizer was sold from the get-go as something to generate musical harmonies. Let’s face it, Harmonizer is a great name.

Whatever the reason, the Harmonizer quickly made its way into recording studios around the world. Tony Visconti famously described the H910 to David Bowie and Brian Eno: “It fucks with the fabric of time!” Visconti used the H910 while recording Bowie’s “Low,” where it was used to create a snare drum sound that descended downwards, with the amount of pitch bend determined by how hard Dennis Davis hit the snare:

The snare sound also has some sort of gating on it, but you can clearly hear the Harmonizer on the first snare hits. The H910 was set to a downshift setting of around -1 semitone, and the feedback was turned up to get the quick delays that shoot down in pitch.

One of my personal favorite examples of harmonizer (ab)use is “Duck Stab” by The Residents. Practically every song on this record uses harmonizer feedback, either for generating a detuned chorus on the vocal, or a minor third transposition with feedback to create “dimished” harmonies. Enjoy the following super creepy video while listening to the nifty pitch shifting tricks.

About the author:

Sean Costello is the “algorithmic reverb plugin wizard” [citation needed] at Valhalla DSP.

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