HOW-TO: Classic Harmonizer Effects, Plug-In Style

Re-create iconic rock sounds with Universal Audio's H910 plug-in
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Developed in 1974 by Tony Agnello and released the following year, the Eventide Clock Works Model H910 was arguably the first commercially available digital effects processor. Offering up to 112.5 ms of delay time with adjustable feedback, and ± one octave of pitch change, it produced an impressive variety of unprecedented sounds. Although the H910 employed digital logic and primitive RAM memory, there was no software (DSP chips were still several years out), and filtering, companding, feedback, pitch change, and mixing were all handled in the analog domain. The H910’s tuned LC clock was also notoriously unstable—resulting in random modulation shifts and other “glitches”—and its A/D and D/A converters were crude by later standards.

It was that unique combination of circuitry that endowed the H910 with its singular sound, however, and Eventide painstakingly modeled all of those quirky characteristics when engineering the H910 Harmonizer plug-in for the UAD platform. The base H910 retailed for $1,500; another $365 got you a second output and a Pitch Ratio readout (I’ve never seen one without this “option”), and if you wanted a more musical way of selecting pitches than dialing in ratios manually, optional monophonic and polyphonic keyboards were available at $500 and $600, respectively.

The H910 plug-in is the equivalent of a fully tricked-out hardware unit with the monophonic keyboard. The H910 was used on countless records during the mid-to-late ’70s (and beyond), including David Bowie’s Low, produced by Tony Visconti, who used the box to add rubbery low thuds that descend in pitch to Dennis Davis’ snare hits. The effect is particularly evident at the beginning of “Sound and Vision”: Each hit retriggers the modulated pitch, and the intensity and depth of the effect appear to be at least partially governed by the dynamics of the playing.

Fig. 1. Re-creating the rubbery thump of Dennis Davis’ snare hits on David Bowie’s “Sound and Vision” with the UAD plug-in. The sound may be approximated on the UAD plug-in by setting the controls as indicated in Figure 1. (In all examples the H910 is on an Aux track, with the Mix control set to 100 percent effect.) The base pitch is one octave down, there’s enough delay time and feedback to create the pitch modulation, and the Envelope Follower provides the dynamics. Adjusting the Envelope Follower parameters, the time relationships between the outputs for Delay 1 and Delay 2, and the Feedback level can result in some wild variations.

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Fig. 2. Approximate engineer Tony Platt’s fat snare sound on AC/DC’s Back in Black. The H910 was also frequently used to fatten up snare hits in less obvious ways. For example, engineer Tony Platt used the device all over AC/DC’s Back in Black album, detuning to a ratio of about 93, with the Feedback and Anti Feedback controls turned up. It isn’t clear what his delay and other settings were, but you can get close with the settings in Figure 2. Platt kept the effect well below the track in his mixes, but try bringing it forward a bit for modern styles, at least on, say, choruses or bridges to increase the energy.

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Fig. 3. Create your own version of the dual-H910 effect used in the ’80s on Steve Winwood’s vocals and Eddie Van Halen’s guitars. Another classic technique involved using two H910s in tandem, panned hard right and left in a mix with the dry sound in the center. Engineer Tom Lord-Alge used dual H910s in this way on Steve Winwood’s vocals on his song “Back in the High Life Again,” and Eddie Van Halen used the technique to process his guitar in the late 1980s. In Figure 3, the Harmonizer Pitch Ratios are set to 0.97 (left) and 1.02 (right), and the delay times are quite short (about 30ms), which closely approximates the sound—but try modifying these and other parameters to create more extreme versions of the effect.

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The UAD Eventide H910 plug-in is obviously capable of many more sorts of effects than these iconic sounds. In Part 2, I’ll share some examples of sounds I’ve crafted, including some that employ DAW automation and MIDI control.