Listen to Frank Ocean’s recent cover of “Moon River,” and you’ll hear a multitude of effects employed to filter, detune, and modulate his rich, layered voice. Modern producers have an arsenal of tools to craft sophisticated vocals, but at one point it was considered revolutionary to simply double a vocal recording.
In this article, I will dive into the storied history of vocal doubling with reference to the important figures and songs that shaped the now-ubiquitous production technique.
At every major juncture in pop music history, musical minds have both relied on and shaped available technology to realize their ideas. As far as vocals are concerned, the ability to record one take, then enhance it with a second for a fuller sound, is largely indebted to the studio experiments carried out by Les Paul—best known today for the Gibson guitar that carries his name—and his wife Mary Ford in the late 1940s and early 1950s.
If you listen to popular music of the 1920s and 1930s, it has an honest quality to it, partly due to the way it was recorded, with all the singers and band members performing together in the same room. You either got the take or you didn’t, and there were no alterations after the fact. A musical recording was supposed be as close to the “real thing” as possible, as if the coolest big band was playing right in your living room.
Unsatisfied with this approach, and in search of new sonic treatments, Paul recorded his guitar playing to acetate disk, then played a new part overtop as he copied one disc to another, repeating the process at different speeds and with delays to deliver a multilayer recording. Dozens of discs were required to produce a final mix.
This overdubbing technique, titled “sound on sound,” was transferred to mono tape machines once they were available, and produced Paul and Ford’s 1951 release “How High the Moon,” one of the first pieces of recorded music to include doubled vocals. Ford also harmonizes with herself at the end of the song. For a total nugget of music history, watch Paul and Ford demonstrate their recording process of the song on live TV in 1953.
It is worth noting that In 1949, Patti Page sang both vocal parts—due to a lack of money for backup singers—on her song “Confess” using the “sound on sound” technique, but the vocal parts were not sung in unison, in true vocal double form.
Multitrack and ADT
In the years that followed “How High the Moon,” vocal doubling became commonplace in pop (a genre still in its infancy) as musicians like Buddy Holly took a greater interest in the technology of recording. On his 1957 song “Words of Love” you can hear two vocal recordings, one of them slightly delayed, to give the impression of density and depth.
By the early 1960s, most major American and British studios were using three- and four-track recorders that enabled adjustment of individual track level, tone, and effects. This meant that pop recordings were no longer restricted to being a straightforward live performance. Instead, studio techniques that deliberately enhanced or manipulated sound grew in fascination with multitracking.
Vocal doubling was one such technique. The subtle timing and pitch differences between two takes—since they can never be quite the same—produce a unique, thickening effect when combined. This effect was the secret sauce behind the sound of the two biggest bands of the 60s, The Beatles and The Beach Boys, who used extensive vocal doubling right from their first releases in 1963, “A Taste of Honey” and “Surfin’ in the USA,” respectively.
In fact, The Beatles recurrent use of vocal doubling over their first five albums led their engineer at Abbey Road, Ken Townsend, to invent a system which could reproduce the effect electronically. In addition to being a time consuming process, recording a second vocal take took up valuable space on limited tape machine tracks. These were the strictly analog days, after all. “Artificial double-tracking” or ADT for short, involves feeding a vocal from one tape machine to another, delaying the tape speed of the second, then combining both versions from the mixer. Like magic, a double tracked vocal without the need for a human retake or two seperate tracks was achieved.
Better yet, The Fab Four discovered that varying the delay time of the second tape machine by hand produced some exciting results. See, a natural-sounding ADT vocal is achieved with a delay of about 20 milliseconds. However, with a shorter, continuously varied delay between 1–10 milliseconds, the two signals produce a sweeping effect as they fall in and out of sync with each other, known as phasing (from 1–3 ms) and flanging. It didn’t take long for the Beatles to become heavily reliant on ADT and its bonus effects to explore new areas of creativity, as evidenced by the psychedelia of their 1966 album Revolver.
Originally, Revolver was mixed in mono, like most other albums from this era. As the recording industry shifted toward stereo reproduction, doubled vocals were panned left and right to create a more expansive feel, as if separate vocals were on either side of the stereo field. Listen to “Love To You” in mono and then compare it with the stereo remaster to hear this splitting technique.
To come full circle, while Abbey Road and ADT techniques popularized phasing and flanging, Paul (Les not McCartney) came across these effects while carrying out his acetate disc recording experiments in the 50s.
Ken Townsend’s ADT remained the de facto studio technique for simulating double tracked pop and rock vocals until the arrival of digital delay effects in the early 1970s, initially as rack mount units, then foot petals with improved technical controls like pre-delay, pitch modulation, and cabinet modeling. Music history nugget number two: a 1976 vocal doubling demo with one of the earliest digital delay units, the Lexicon Delta-T.
Around this time, the commercial availability of electronic instruments like the synthesizer and vocoder also enabled artists to explore robotic vocal textures and new means of vocal expression. A blend of the unmodulated voice and vocoded voice that was equal parts funky and futuristic set the template for the signature sound of many artists between 1975-1985, including Kraftwerk, Roger Zapp, and Herbie Hancock.
Today, you don’t need to look much further than a trending Spotify playlist to hear a variety of vocal doubling techniques, often within the course of a single song. Although the end result differs, its common for modern pop, rap, and R&B artists to employ doubles and triples using a mixture of delay, reverb, and pitch correction for a wide stereo effect.
Available for closer listening as acapellas, Katy Perry’s “Wide Awake” and “Firework” reveal a common, but oh so effective vocal stacking technique. Her vocal line is doubled with the above-mentioned effects whenever the song title is repeated in the verse and chorus, emphasizing its importance to listeners and making it memorable.
For a balance of warm and cool energy, producer-rappers Travis Scott and Post Malone typically combine at least one layer of thick, saturated vocals with a synthetic, pitch-corrected one. In a genre where it's common to have two or three featuring artists on a single song, vocal doubling effects change accordingly. For example, in Scott’s recent “Stop Trying to be God,” the dubbed out delay and distortion coating his own voice is reeled in when James Blake sings his part.
With less reliance on major labels for success and an ever-evolving set of technical standards, there are no hard-and-fast rules for vocal doubling. Some still prefer to keep vocal takes au natural, whereas others chose to multiply their voice with musical gloves.
I hope this short recording history lesson has provided you with some inspiration for your next vocal session!