Pro Audio

Double tracking and modulation pedals that emulate classic tape techniques

Exploring the depth and character of double tracking: A versatile, innovative studio technique in pedal form.

Double tracking makes your track bigger and imparts a colour unachievable with a single voice. It can be used to create a thicker sound to deliver extra sheen to a mix, or to inject an ethereal, psychedelic vibe through modulation and phase cancellation.

So, in time, double tracking and more tonally colourful varieties like flanging and chorus were converted into stomp box form for guitarists to utilise on the go. In this piece, we’ll dive into the how double tracking methods evolved into pedals and discover that like modern reverb and distortion, double tracking and modulations pedals are informed by techniques originated in the studio.

Double Tracking

Manual Double Tracking

The traditional approach to double tracking means getting the musician to do their part once, and then record again on an adjacent track, playing along as if they were two people. It gives a bigger, deeper, richer sound, and can be executed so well that it sounds exactly like a single performance with two people. Elliott Smith began his double tracking experiments with a four-track and a Shure SM57 – it became inextricably linked with entire musical output.

Back when recording on tape was the norm, it was quite costly and time consuming to do this – the cost of tape, the manual labour of mixing down multiple takes and changing reels was quite a challenge. It is still done today, but with much more ease. We can do it at home with a single mic and all the digital tracks a computer can handle.


Automatic double tracking – ADT for short – is an analogue technique used to create the double tracked sound without recording two tracks manually. It was pioneered by Ken Townsend in the 1960s at Abbey Road Studios. ADT uses the same techniques as tape delay to create an oscillating delay that is then combined with the original sound source.

The Beatles have a hefty amount of their discography affected with ADT, so if you dig that sound, you’ll be keen to have a play with some of these pedals that attempt to mimic this effect authentically. The TC Mimiq Doubler and Keeley 30ms Automatic Double Tracker are examples of pedals where engineers have gotten the ADT sound right.


The flanging technique is a more tonally extreme double tracking approach. It involves mixing two identical signals together – the second signal is played at a variable distance away from the first. The changes over time create phase cancellation, as the peaks and troughs of certain frequencies coalesce and diverge.

The sound can be described as a ‘swoosh’, ‘jetplane’ or ‘underwater’ tone, and has been a favourite among psychedelic and heavy rock acts such as Pink Floyd and Radiohead. Because of its popularity with guitarists, the sound of a flanger had to be developed into a stomp box to make it portable and live.

While the origins of flanging can be attributed to Les Paul’s phasing experiments with acetate disks on turntables running at different speeds, the use of the technique as it is translated to guitar pedals comes from tape.

As the technique matured, tape flanging consisted of the finished track being recorded to two matching tape machines, then replayed with both running concurrently. A finger is placed on the rim (otherwise known as a flange) of the reel to slow it down, and another recorder then records the resulting sound – it can be levelled out again by pushing the other reel with the same pressure.

Some of the early pioneers stompbox flangers include the classic MXR Flanger, the Electro Harmonix Electric Mistress and the Boss BF-3. Yet modern models like the Strymon Deco and Catalinbread Zero Point take a very literal interpretation of the method, with controls with controls to manipulate lag time and giving users the experience of operating two tape machines.

Stereo Flanging

As tape flanging was being developed, so were stereo recordings, so it makes sense that these crossed paths. The stereo field immerses the listener more deeply and making it feel like being in a wind tunnel while the music coalesced around you.

One of the early pioneers of the stereo technique was Eddie Kramer: he used the method to dramatic effect on the outro of Bold As Love by Jimi Hendrix. The flanger exacerbates the already metallic texture of of the drum kit especially. It became somewhat of a classic rock trope to flange drum fills in particular to create a sense of swirling psychadelica in stereo setups.

To get the most out of the creativity of the effect, pedals were created that utilised the stereo field. Pedals such as the ARION SFL-1 Stereo Flanger, Electro-Harmonix Stereo Electric Mistress, and TC Electronic Vortex Stereo Flanger take full advantage of the sonic field.


Some flanger sounds can be mistaken for a chorus effect, mostly because they work in a similar way. A chorus sound is inspired by a choir – multiple sound sources singing the same pitch, but not perfectly, so the changing delay is evident.

The dry signal is mixed with the second wet signal with its changing delay like the flanger, but a low frequency oscillator is added. The resulting sound is lush, big, and emulates a realistic performance – where humans don’t play in time or on pitch absolutely perfectly.

Chorus pedals have enjoyed a profound history adding shimmer to guitar sounds, especially in the 70s and 80s. It’s hard to go past the classics from BOSS, though most major manufacturers have their own versions of this incredibly popular effect.

It’s hard to imagine the array of effects that the combination of two tapes machines spawned throughout the decades. Complex and compelling sonic artifacts are introduced when layers of sound – even if they are identical sounds – are combined into a single mix.

The airy texture of straight double-tracking, the sea-sick swirl of chorus and the sci-fi sensation of flange are manipulations of a utilitarian, yet essential recording medium: tape. This all makes it doubly magical to conveniently access these sonic varieties with a stomp on a pedal.