Automatic double tracking has been a staple in studios since it was pioneered in the 1960s at Abbey Road Studios.

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Today, of course, many plugins produce natural and convincing double-tracked vocal effects that go beyond the original tape-delay-based versions of the 1960s.

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So, let’s take a look at how to create that classic automatic double tracking effect used on classic Beatles records.

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Later on, we’ll also dive into a few modern tools that take the technique to the next level.

What is automatic double tracking?

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Automatic double tracking (ADT) was a studio technique developed to artificially double vocals on analog tape delay machines at Abbey Road Studios as requested by The Beatles in 1966.

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It uses a tape delay machine that delays a vocal signal slightly from the original and uses a low-frequency oscillator (LFO) to adjust the amount of delay slightly.

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When mixed back into the original vocal signal, the oscillating delay time creates a natural-sounding resonance that wavers similarly to the human voice, creating a fairly convincing vocal doubling effect.

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If you want to produce that classic ADT effect, you can easily create one with stock plugins included in most DAWs. All you need is a tape delay plugin and an LFO plugin, or a phaser-flanger with those capabilities.

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Here’s how to create a classic ADT-style effect with stock plugins in Ableton.

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Use Ableton’s Phaser-Flanger plugin on your vocal part

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Phaser and flanger effects are closely related to doubling and were also pioneered using tape machines. They all play around with audio phase and short delay times.

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For this article, we’re using Ableton’s ADT-style doubling effect, which is found inside of its Phaser-Flanger plugin. Here’s how it sounds when you open it up.

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But later on I’ll share a few other doubling effects plugins to try on your own.

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With the Phaser-Flanger plugin open and the doubler setting selected, you’ve now set up a doubler effect. However, you may want to adjust the doubler’s settings to taste.

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The three main settings that control your ADT effect-style vocal are phase, delay and LFO. 

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Here’s how each setting interacts with the ADT-effect in more detail.

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Delay settings for automatic double tracking

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Delay is what makes ADT possible. To create the effect, a vocal signal is split into two stereo left and right channels. 

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One channel is kept untouched while the other is sent through a delay effect. In most cases, a short delay time of 20-35 milliseconds is used, creating a slapback-style delay.

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In most doubler plugins, you’ll see a time setting that you can adjust to taste, with short delay times being less noticeable to the listener and longer times producing an increasingly echo-y sound.

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If the ADT effect has feedback settings, you can use them to feed some of the delay effect back into the original signal, creating even more echoes. 

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But in most cases, ADT should have little to no feedback, since the idea is to shift a single vocal into a doubled sound, not create an echoing vocal part.

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Automatic double tracking low-frequency oscillators

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The low-frequency oscillator (LFO) is what makes the ADT effect possible. Without one, all you have is a tape echo with a short, slapback delay time.

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When an ADT effect splits the signal and sends one half to a short delay, the delay time is modulated with an LFO.

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These constant shifts in delay time affect the delayed signal’s pitch, producing a wavering effect with slight pitch variations that mimic a naturally doubled vocal part.

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In most automatic double tracking LFO settings, you get a frequency knob that controls LFO cycle speed and an amount setting that controls how much the LFO is applied to the incoming vocal’s delay time.

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There may also be settings to change the LFO’s waveform, which changes the way it interacts with your incoming signal.

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Increasing the frequency of the LFO creates an increasingly wobbly vocal double, while the amount setting adjusts how much the doubled vocal goes in and out of pitch.

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To create a more natural-sounding automatic vocal double, keep the LFO at a lower frequency, ideally 0.01-1 Hz, while also keeping the delay modulation amount setting low.

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Adjusting the phase of an automatic double-tracking effect

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Phase is the final setting to adjust in most automatic double-tracking effects tools.

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The phase setting is used to control the amount of stereo offset between the original signal and the second doubled and delayed signal.

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At 0° of phase, both channels are aligned, resulting in no changes to the overall sound.

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Adding degrees of phase offset will offset the left and right channels, creating a stereo widening effect that can make the doubled vocal sound wider and bigger.

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Automatic double tracking plugins

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Many plugins offer automatic double tracking features.

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Aside from Ableton’s relatively simple Phaser-Flanger plugin, let’s take a look at some other automatic double-tracking plugins that offer more advanced features.

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1. Revoice Pro 5

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Revoice Pro 5 isn’t like any other vocal doubler on the market right now, and it’s arguably the best and most convincing one out there.

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Don’t take our word for it, Production Expert called it the best doubler for creating natural, human-sounding vocal doubles.

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“Revoice Pro 4, this represents the best ADT we’ve heard.” - Production Expert

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That’s because Revoice doesn’t use the traditional modulated tape echo ADT signal chain.

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Instead, it adds powerful formant shifting, vibrato and pitch correction tools to the standard delay and modulation effects used in ADT.

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The addition of subtle modulation to both the formant shift and vibrato on the doubled vocal is why Revoice creates the most convincing automatic vocal doubles right now.

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You also get the option to create doubles in mono and stereo alongside some great, professionally dialed-in presets.

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Of course, Revoice is much more than just a vocal doubler. It can also automatically align vocal stacks and it includes a powerful graphic pitch correction suite.

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Here’s an in-depth tutorial about the vocal doubling feature in Revoice.

2. Abbey Road Reel ADT

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Abbey Road Reel ADT from Waves is possibly the most true-to-form classic ADT effect out there.

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Its name and user interface pay homage to the reel-to-reel tape machines that were used to pioneer ADT at Abbey Road Studios, and it produces a faithful recreation of the original effect.

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If you’re looking for that classic ADT-style vocal effect used on so many classic rock albums, this plugin is well worth your attention.

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3. iZotope Vocal Doubler

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iZotope’s free Vocal Doubler tool is a useful but basic tool that works well for basic ADT use cases.

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If you don’t have a dedicated ADT plugin or tool in your DAW, this one is worth downloading and trying for free.

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4. Antares Duo

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It makes sense that the creator of AutoTune, Antares, also has a doubler plugin on offer.

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The plugin features simple controls that help you produce a decently convincing double, but it doesn't nearly offer the same depth of control as other paid plugins like Revoice Pro.

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5. Ableton Phaser-Flanger

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Ableton's Phaser-Flanger includes a simple doubler feature and an intuitive interface. It made a good candidate for showing how ADT works in this tutorial.

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If you have Ableton already, this plugin is a great option for basic ADT effect tasks.

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Automatic Double Tracking is here to stay

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From its pioneering days at Abbey Road to today's advanced digital tools, Automatic Double Tracking (ADT) remains an essential technique for adding width and depth to vocals. 

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The classic effect is achievable with just a short tape delay (20-35ms) and subtle LFO modulation (0.01-1 Hz) using your DAW's stock plugins. 

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But, for those seeking the utmost realism and control, dedicated plugins like Revoice Pro 5 or the authentic Waves Abbey Road Reel ADT offer enhanced features to master this timeless vocal doubling trick.

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Good luck crafting your next automatic vocal double!

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