FLASHBACK #4.1: THE H910 Harmonizer - 1975 (w/ FLASH SALE)

[Orville71]

Please read our latest blog in which we teach about the history of pitch change:
https://www.eventideaudio.com/blog/aagn ... harmonizer

Excerpts from the blog:
There’s a lot of history to cover about the conception and development of the Harmonizer so let’s first consider the underlying principle: the interesting phenomenon known as Pitch Change.

The Strange Case of Pitch Change

While Pitch Change is naturally occurring, throughout history, humans would rarely have perceived the effect because the sound source must be traveling at a high enough rate of speed relative to the listener to cause a discernible change in pitch. Why had no one elucidated this effect in our long history? It’s simple; few things moved fast enough! Sound travels at ~750 mph. To notice even a slight pitch change of 2% a sound source with 100% constant pitch would have to be approaching the listener at 15 mph. (Kids whirling objects around on a string were not the scientific observers for which one would have hoped.)

In 1842, Christian Doppler suggested that “the observed frequency of a wave depends on the relative speed of the source and the observer.” Doppler was thinking about star light, not sound, but a wave is a wave is a wave.

Just three years later, Buys Ballot, a Dutchman, demonstrated the Doppler Effect on sound waves by having six tubas play the same sustained note while perched on the front of a speeding locomotive.



Read more about the history of Pitch Changing: https://www.eventideaudio.com/blog/aagn ... harmonizer

The H910 Harmonizer plug-in is on sale until May 3rd, 2021. Try the 30-day fully-functional demo.
https://www.eventideaudio.com/products/ ... 910-plugin

[Orville71]

Today we have Flashback #4.2 - The H910 Harmonizer - The Product!


The H910 was arguably the first pro audio digital effects product. Prior to its introduction, studios had adopted digital delay as a utilitarian tool to replace the bother of using an expensive tape machine (and salaried tape op) for double tracking and plate reverb pre-delay. Eventide’s DDL1745M had an optional pitch change module and a handful of studios began to discover digital effects. However, the interface was not designed to easily dial in pitch-related effects, and there was a technical challenge to overcome.

The Challenge: Pitch Change Without Speed Change
By 1975, IC technology had sufficiently advanced to the point that it became practical to design a digital pitch change effects box — the H910. Random Access Memory ICs became commercially available and pitch change was made possible by reading the audio from memory (playing back) at a different rate than writing (recording). This is the equivalent of recording to tape at one speed and playing back at another speed. Of course, as with tape, the audio plays back at a faster or slower rate.

The challenge for a real-time pitch changer that does not change tempo is rather obvious. If you increase pitch by continuously reading from memory faster than you write to it, you’ll run out of data. If you continuously read from memory slower than you write to it, the delay will grow until you’ve completely filled up the memory. It helps to think of this as increasing pitch by decreasing delay and decreasing pitch by increasing delay. Delay can’t decrease past zero (that would require a magical digital “advance” line). Nor can delay be infinite. In fact, for real-time performance, it’s best to limit maximum delay to no greater than ~20 msec.

The Circular Delay Buffer
The ‘solution’ is both simple and imperfect. Use a ‘circular delay buffer’ of some length (typically 20-30 msec) with the delay abruptly jumping from zero to max in the case of increasing pitch (decreasing delay) and from max to zero in the case of decreasing pitch (increasing delay). Of course, the instantaneous jump results in a “discontinuity” in the audio signal. We called this the ‘glitch.’

The Glitch
What does the glitch sound like? How noticeable is it? Well, that depends on the pitch ratio and the audio source. For pitch ratios close to unison (pitch ratio ~1.00), the delay changes slowly and glitches occur infrequently. As the pitch ratio moves away from unison, the glitches occur more and more frequently. Since the audio on each side of the discontinuity cannot be controlled or determined, these glitches can be quite nasty, full scale clicks or complete drop outs.

Read the entire blog here: https://www.eventideaudio.com/blog/aagn ... er-product

[Orville71]

Today we have Flashback #4.3


Minds. Blown. Good. Evil.
The H910 has rightly been described as ‘groundbreaking’, ‘iconic’, ‘mind-blowing’ and more. Looking back nearly 50 years, it’s hard to appreciate its impact and so we reached out to some of the earliest users and asked how they remembered their first encounter with pro audio’s first digital effects device.


https://youtu.be/977Sri5EcCE

Read the entire blog to learn about how the H910 was used in the movie Star Wars! https://www.eventideaudio.com/blog/aagn ... inds-blown