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Many of the earliest electronic instruments base their human interaction around the familiar piano keyboard. We find this in the 1897 Telharmonium and the valve organs of the early 1900s. However, there were also some different ideas swirling around in the soup of early electronics. The 1928 ondes Martenot altered pitch using a metal ring worn on a finger to slide along a wire. The theremin, invented around the same time, got rid of physical surfaces altogether, and required the player to place their hands in space between two antennae to pull pitch and volume seemingly out of the air.
While the piano keyboard paradigm persists, many designers found the keyboard limiting in terms of pitch and frustrating for people who weren't accomplished players, and so as electronic instruments developed, alternative ways of interacting with them were sought.
Perhaps the most successful of these are touchplate controllers—now fairly common in the world of commercial modular synthesizers. They often borrow from the keyboard in terms of layout, but the interaction is very different. The touch plate involves you in the circuitry. You become a source of capacitance or a variable resistor that ultimately affects the voltage used to control synthesizers.
Early Touch Plate Controller Designs
Don Buchla is often credited as the inventor of the touchplate controller, which first appeared in the Buchla 100 series Modular Electronic Music System. It was a system commissioned by composers Morton Subotnick and Ramon Sender of the San Francisco Tape Music Center, ultimately featured on Subotnick's 1967 album Silver Apples Of The Moon. Buchla purportedly drew on his experience working with similar systems for fuel sensors at NASA, but there was an earlier inventor of musical machines whose own touchplate control surfaces predate Buchla's: Canadian scientist and composer Hugh Le Caine.
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Le Caine had been building extraordinary electronic instruments since the 1930s. Most famously, perhaps, was the fascinating Electronic Sackbut. It was perhaps the first voltage-controlled "synthesizer" ever made, but it is impossible to replicate due to its prototype nature, which was built on, fiddled with, adjusted, and built on again and again over many years. Le Caine was fascinated with musical expression, and his junkshop keyboard was sensitive both vertically in terms of volume and vibration, and horizontally in terms of vibrato. His work with the Canadian National Research Council led him to develop technology for emerging electronic music studios at the University of Toronto and Montréal's McGill University. He spent decades developing technologies that we now take for granted. [Ed. Signal will soon cover Le Caine's work more extensively in dedicated articles.]
Regarding touchplate controllers, Le Caine came up with the Printed Circuit Keyboard, c. 1962. It generates voltage via the conductivity of the player's fingers as you connect them between the squares. Initially, it was laid out like a regular keyboard, but as the squares could be tuned individually to any pitch or frequency, the regular 12-note scale became irrelevant. Composer Richard Henninger reflected on his time spent playing the Le Caine's inventions at the Toronto University in an article on eContact. Describing the controller, he said:
"You could determine the pitch of each pad, tuning them to almost anything, and then zip around the surface with your finger, gliding effortlessly from sound to sound. All kinds of cool gestures could be performed on the instrument to produce glissandos, arpeggios and sound bursts, which at that time were impossible to achieve any other way."
Returning to Don Buchla and his early collaborators, they wanted to break free from the constraints of keyboard music. Touch plates were perfect for this venture. He said:
"They were all capacitance-sensitive touch-plates, or resistance-sensitive in some cases, organized in various sorts of arrays…I saw no reason to borrow from a keyboard, which is a device invented to throw hammers at strings, later on, for operating switches for electronic organs and so-on. A keyboard is dictatorial. When you’ve got a black and white keyboard there it’s hard to play anything but keyboard music – And when there’s not a black and white keyboard you get into the knobs and the wires and the interconnections and timbres, and you get involved in many other aspects of the music, and it’s a far more experimental way. It’s appealing to fewer people but it’s more exciting."
Early Buchla designs used resistance detection-based touch plates relying on the resistance of the musician’s skin. The touch plate was electrified with a positive voltage, and you'd use your finger to bridge the gaps and complete the circuit. However, it wasn’t considered ideal to have your fingers dabbling around in 15V all day long, and the skin's resistance proved to be very varied and unreliable. Capacitive touch-plates, similar to Le Caine's, became the better choice.
How do They Work?
So, what exactly are we talking about here? Touch plates work by using your body to complete the circuit. That's why touch plates are not solid strips of copper but grids, teeth or interwoven groovy designs that allow a single finger to bridge the gap and complete the circuit. You can make the connection with different fingers or different hands, and the amount of body we get in the way affects the voltage being generated.
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[Above: a Buchla 112 tactile controller, part of the original/prototype Buchla 100 Series system at Mills College. Image via Sarah Belle Reid.]
In the simplest terms, in capacitance touch-plates, our skin/fingers/flesh act as a capacitor, storing small amounts of charge in the form of static, which changes the capacitance of the circuit, altering the voltage at the output. This voltage can then control various parameters on modular synthesizer modules. Often, the connection can just form a gate that allows the flow of a voltage set elsewhere. In other circuits, the voltage generated by the interaction is used as the modulator. We tend to call this pressure sensitivity because the harder you press, the more skin acts on the plates, so the more capacitance is in operation.
It's interesting how this simple interaction with a very simple circuit provides a level of nuance and control that's very different from a piano keyboard. It's the position, movement, and pressure of your fingers that are generating voltage, which is much more akin to MPE control on some modern MIDI controllers—albeit with more crude, simple technology. Touch plates provide a very creative way into musical expression without having to be a pianist. They are not restrained by pitch or a correct way of doing things; they are to be experimented with and enjoyed like any other part of a synthesizer, and that's why they persist to this day.
Modern Touch Plate Controllers
Modern touch plates don't vary much from their origins. Sometimes, the simplicity of the copper plate circuit is replaced by interactive materials and touch-sensitive surfaces, but the concept is still the same. Let's check out some modern possibilities.
The Buchla USA LEM218 v3 is a good place to start, as it’s a direct descendant from the touch-plate controllers from the original Buchla modular 100-series system, the System 200 series, and most famously, the Music Easel. It's laid out like a piano keyboard, allowing for an unconventional means of interacting with familiar musical concepts. However, the controller has a row of four "Preset Voltage Source" pads that can be tuned individually to either provide transposition to the whole controller or to act as a little four-keyed controller by itself.
The surface is very sensitive, allowing you to produce pitch, gate, and infinite variations in pressure with a single touch. It's monophonic for voltage purposes, although it can be fully polyphonic over MIDI. Another touch strip on the left provides portamento and vibrato so you can slide between notes and pitch shift from the original finger position. The keyboard, Preset Voltage keys and slide strip all have independent CV outputs which, along with an arpeggiator, make it a very versatile controller.
Verbos has its own version of the 218 called simply the Touchplate Keyboard. They've ignored MIDI and stuck straight with generating Eurorack-compatible CV. It has the same pitch, pressure, and gate outputs and the ability to bend notes. Instead of the four Preset Voltage pads, it has eight tune-able touch pads that provide a completely piano-free experience. If you like the idea of leaning into a piano-free controlling experience, then perhaps the strangely-named Mini Horse from Verbos would be more to your liking. It has twelve pads that can be individually tuned to any voltage, and each has its own position, pressure, and gate output. So, each pad is its own little controller, as well as combining into a playable surface.
Make Noise has explored Buchla's touchplate concepts in their Pressure Points and Rene modules, but most recently, they've pulled them into their 0-Ctrl keyboard and sequencer. You have eight tuneable pressure pads that can act just like the original Buchla controller. But then Make Noise gives it the ability to automate and cycle into a fascinating sequencer—much like the 1970s Serge TKB touchplate controller/sequencer. On 0-Ctrl, each step can have its own duration and strength controls, with "strenght" controlling an envelope and variable gate generator, giving changes not just in pitch but also in signal levels.
Intellijel takes a different technological approach with their Tetrapad controller. It uses force-sensing resistors to read both pressure and position on four touch-sensitive strips. The digital brain gives it multiple modes of operation to offer voltage levels, gate outputs, sequencing, chord generation, LFOs, or switching.
Sound Machines have been experimenting with alternative controllers for a long time. The LS1 is a brilliant little single-strip controller that outputs gate and up/down position when you place your finger on the surface. Hold the "Rec" button, and you can record up to eight seconds of movement for custom automation, LFOs and sequencing. This idea has been quadrupled into the T-Quadstrip, which lets you switch between four individual controllers with a single strip. Soundmachines' T-Series of modules features the same strip built into an oscillator, spectral processor, and formant filter for excellent integrated modulation.
However, for the ultimate in control, you should check out Soundmachine's Arches. It brings together numerous touch controllers into a single device. It's nicely designed to follow the fall of your fingers and has shades of the Buchla Thunder controller. In total, it has 32 CV outputs taken from eight lightstrips, two XY pads, four controller strips, and numerous buttons. It's very configurable and also outputs MIDI over DIN, USB, and Bluetooth.
In the exuberant Voltage Lab 2, Pittsburgh Modular included a Touch Controller keyboard and sequencer. This is a fully digital affair with multiple functions and lanes of interaction. There are 16 pressure-sensitive touchpads that can output pitch CV on a red or yellow channel controlled by the appropriately colored knobs, and modulation CV on a blue channel. The sequencer mode has loads of interesting avenues to go down with chance and probability, range, direction, patterns and cycles. You can split and layer the keyboard, or use it to scale expression and other parameters. Pittsburgh has built in a mind-boggling array of functionality into a very simple interface, which enables some very versatile control over the rest of the Voltage Lab 2 or anything else you patch it into.
If you don't mind a bit of digital complexity, then Bela Gliss open-source touch controller might be for you. It appears as simple as the Soundmachines LS1, but through some clever finger gymnastics, it can switch to a wide selection of modes and happenings. It generates pressure, position and gate CV and can be a simple generator, a modulation recorder, a positional keyboard, a signal visualiser, and more. Being open-source, it also has a habit of reinventing itself and finding more modes and ways of being.
All in all, touch controllers offer a different approach to the piano-style keyboard, not just in the playing but in what you can do with your fingers to change and disrupt things once they are on the surface. Modern materials can bring additional functionality, but really, the touch and the press with the fingers is enough to bring delight to synthesizer interactions that ignore your musical training and let you express yourself more directly with your voltage-driven instrument.
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