The expression pedal has got to be one of the coolest inventions in the world of audio effects. With an expression pedal, you can totally change the sound of an effect by rocking your foot back and forth on a treadle – like a wah-wah, but on any knob! This power has allowed guitarists a greater degree of sonic expansion and has brought the guitar closer to the dynamic range of a vocalist, woodwind, or synthesizer!
But where and when did the expression pedal emerge? Who were some pioneers of the expression pedal? And, most importantly, what are examples of contemporary guitar effects pedals that are either based on or expanded by the expression pedal?
The modern expression pedal is rooted in the pedals found in nineteenth and twentieth-century pipe organs. As the technology developed and the number of pipes on the organs grew, it became common to enclose some of the rows into a wooden box called a swell box. Mechanical wooden shutters were built into the boxes and the performer could open or close the shutters with a foot pedal called a swell pedal to adjust the volume of the organ.
With the introduction of electricity, the role of the expression pedal expanded beyond just volume control. Effects like wah, tremolo, and uni-vibe emerged in the 1960s and the expression pedal suddenly could control filters, rates of modulation, and whatever the Ludwig Phase II Synthesizer was doing – as made popular by Sonic Youth on ‘The Diamond Sea’.
Today, expression pedals are used to control a wide array of variable parameters on amplifiers, stompboxes, and rack effects. Expression pedals can be whatever variable the designer dictates, or a circuit-bender can figure out!
Pioneers of the Expression Pedal
Expression pedal effects have been pioneered by a number of creative musicians over the years. Perhaps the most iconic pioneer of the wah pedal effect, Jimi Hendrix incorporated the expression pedal on a number of classic tunes including “Voodoo Child”:
The Univibe was unique for being one of the first effects to have an optional (but highly recommended) foot control, Robin Trower is known for using one – most iconically on his 1974 classic “Bridge of Sighs”:
Tom Morello pioneered the use of the expression pedal based effect called ‘Whammy’, which uses the expression pedal to modulate pitch up and down like a whammy bar. His guitar playing with Rage Against the Machine and Audioslave broke open many creative doors for the expression pedal. Here is an interesting interview with Morello about his use of the whammy pedal:
Analog circuits in modernity have benefited from the relatively inexpensive cost of including an expression pedal jack, allowing creatives to expand their control over a favorite pedal without inconveniencing most folks who want something immediate, consistent, and smaller that expression based effects, like wah pedals, usually lack. Troy Van Leeuwen takes full advantage of the filter creatively included on this Moog MF Drive here.
Expanding Pedals with the Expression Pedal
With the proliferation of multi-effect units, the expression pedal has taken on an expanded role in the world of guitar effects. The introduction and development of multi-effects units like the Roland VG-8 and Boss GT-5 and ME-50 forced pedal designers to expand the capabilities of the expression pedal. Since each of those units contains multiple expression pedal effects like wah, univibe, and whammy, it became necessary to design hardware that could switch between and modulate different parameters. Once it was there, they figured it might as well work on the other effects too!
This evolution has led to the contemporary environment where expression pedals are used to modulate all sorts of effects parameters including pitch, filters, speed, depth, rate, mix, delay feedback, reverb trails, etc. Here are a few examples of these insane, new creative tools.
Old Dogs Can Learn New Tricks
Perhaps one of the first effects pedals to introduce additional expandability via expression pedals were Line 6’s 4-button modeler series. The classic “green box” DL4 Delay Stompbox Modeling pedal has proven to be the crown jewel of this collection. The DL4 was first introduced in 2000 and has since become a benchmark delay on many pedalboards.
The DL4 features 5 adjustable parameters. Players can assign two configurations of those 5 knobs to an expression pedal. One preset is at either end, and you can slowly blend between those two settings to explore an entire range of sounds – it is an incredible feeling. This is the modern model for creative digital expression as found in pedals by creatives like Red Panda Lab, Alexander Pedals, and Meris.
Legacy companies have responded to this by adding more expression capability to their pedals, such as Boss, or Electro-Harmonix. To name just a few examples, their Deluxe Memory Man, Memory Boy, and HOG2 Harmonic Octave Generator all feature an expression pedal option.
The digital side of Boutique Pedals has allowed an incredible range of expression-based control. Taking a note from Line 6, modern DSP luminaries like Strymon, Red Panda Lab, and Meris add full assignable expression functions to their pedals. This allows for incredibly creative sound to be found while allowing the hands to do the instrument playing.
Flex Your Head!
Modern development has also brought along lots of unique way to add expression control that don’t involve a foot treadle. Old Blood Noise Endeavors is an excellent example of a brand breaking into utility devices for expression inputs. The Expression Slider is a mixing board style fader in a box. This is excellent for creative remote control of a knob on your pedal, or for assigning hidden parameters in a pedal to a tactile switch.
Taking this concept one step further, Old Blood Noise released the Expression Ramper. This powered device sets an automated signal to an expression pedal input. Imagine a tremolo with rate and depth controls, not instead of the circuit raising and lowering your volume, it is sending that signal to an expression pedal, effectively turning a knob automatically and consistently ramping between two expression settings.
Our very own Andy Pitcher exploring Old Blood’s creative expression machine.
Feet Don’t Fail Me Now
From the early experiments with wah and univibe, to more hi-tech variations from boutique pedal designers, expression pedals can open an entire universe of new sounds for you to explore. If you are in the market for new delay, reverb, flanger, or other modulation effects, look into some options that offer an expression pedal extension. It is a fantastic way to get a little more value out of the pedals you already own. As always, we guitarists can take a cue from our drummer friends and get our feet involved in the game as well!