For the last two years, Queen Mary, University of London Lecturer in Digital Music Dr Andrew McPherson has been working on a system that brings continuous dynamic or expressive control to a piano-style keyboard without having to reach for pitch wheels, buttons, dials or pedals while playing. The TouchKeys multitouch musical keyboard comprises capacitive sensing strips stuck to the upper surface of each key, circuit boards housed within the host instrument that collect all the sensor data, and some custom software running on a connected computer. The system can be paired with any software or synthesizer capable of understanding MIDI or OSC, with the movement of the fingers controlling the kind of sounds produced. Vibrato, for example, could be linked to side to side rocking motion, and sliding up and down a key might alter pitch. McPherson now plans to make the fruits of this university research project available to other musicians by offering self-install TouchKeys kits to crowdfunders.

"As a composer, I'm always interested in finding new sounds and new ways to control sound," reveals McPherson. "My primary instrument is viola, where I'm used to having continuous expressive control over the pitch, volume and timbre of every note. On the traditional piano, though, once you play a note, you have very limited options for controlling its sound before it is released. The TouchKeys project is about trying to maintain the richness of piano technique while adding the kind of continuous control you usually find on string instruments, all while remaining familiar to keyboardists who have spent many years becoming proficient at their instrument."

He began working on the project while he was a post-doctoral researcher in the Music and Entertainment Technology Laboratory at Drexel University, but TouchKeys moved with him to its current home in the Centre for Digital Music in the School of Electronic Engineering and Computer Science at Queen Mary, University of London. TouchKeys is a keyboard controller that can be used with programs like Max/MSP, Kontakt and Reason, or any MIDI instrument.

Peel-and-stick capacitive touch sensor overlays attach to the surface of each white and black key on any standard width keyboard, covering the entire playing surface of the key. TouchKeys is able to support keyboard sizes ranging from 25 to 97 keys. The sensor layer and particularly sticky double-sided tape add only 1.6 mm of extra height to a key, and give the surface a slightly more textured feel and slightly dimpled look.

"The dots are vias in the circuit board which connect the top and the bottom layers," explains McPherson. "They're a part of the manufacturing process but their exact location isn't what makes the system work, and you don't feel them under the fingers either. The important part on the top is the geometry of the sensor pads (crosshatch and zigzag patterns, a little harder to see than the dots). But even though they're a side effect of manufacturing, I do like the look of the little dots."

The sensor strips register location and contact area across the X and Y axes (though that gets clipped to Y-axis only in the space between black keys). Up to three simultaneous touch points per key can be detected, and the system can determine whether you've hit the key with a fingertip, or are using the flat. The white keys have a 256-point resolution in the X axis and a 2,432-point resolution in the Y axis, while the black keys get the same X-axis resolution, but the Y is reduced to 1,536 points. A scan rate of 200 Hz is reported to result in little or no perceived latency.

Each key gets its own small microcontroller. All the sensor strips connect via flat-flex cables to a narrow board that slips inside the host instrument. Each board covers two octaves, so for larger keyboards, controller boards are daisy-chained together to span up to eight octaves. The whole setup draws the power it needs over USB, and the input data is sent to a computer for processing using special software. The system doesn't output sounds on its own, however, and will need to be used with a software instrument or external MIDI synth.

TouchKeys can even be installed on the keys of an acoustic piano, though the setup process is a little more involved. "TouchKeys can be installed on the surface of an acoustic piano, and I've actually done that as part of a research project to collect performance data from classical pianists," says McPherson. "In terms of using the sound from the piano somehow, this would have to be set up externally by the musician – there isn't any 'built-in' sound to the TouchKeys, but it will work with any synthesizer."

The TouchKeys software allows users to control what happens when you shake your wrist or drag your mid-digit. Some presets are included which allow the player to change notes or trigger extra sounds by using two or more fingers to touch a key, for example, tweak parameters like volume and timbre, add more realistic expression to instrument emulations, or use pinch and slide multitouch action to shape sounds. Where pitch wheels influence all the notes at once, the TouchKeys system assigns each note its own MIDI channel for individual control.

The software can currently run on Mac and Linux platforms (Windows users will have to shout out good and loud for a Microsoft-compatible version to be produced), and McPherson is planning to make it available under a GPL open source license to cater for community development, idea sharing and patch creation.

To get the system into the hands of musicians, TouchKeys has launched on Kickstarter. Even though the system can support up to 97 keys, McPherson told us that very few commercially-available instruments actually run to the full eight octaves, so he's offering self-install kits that range from 25 to 88 keys. "I figured that if someone contacted me with a specific project involving 97 keys that we'd talk," he says.

He reckons that most folks will be able to install the system on an already-owned synth in an evening, with just a screwdriver and some get-up-and-go. Though the host instrument will need to be opened up and exposed to the world, installation is solder- and programming-free, and there'll be an illustrated manual and instructional videos to help guide the novice through the process. If you want to check for size compatibility before diving in, templates are available for download from the Kickstarter campaign page.

Once the key overlay strips are attached to the keys, removal is possible, but it's not a simple affair and there's a risk of damage to the sensors. For this reason, the development team doesn't officially support TouchKeys removal. Novation and Doepfer keyboards with the TouchKeys system already hooked up and ready to roll are being made available in limited quantities for those that don't like to tinker, or don't have an instrument available for conversion.

TouchKeys will be made in the UK, and early bird specials start with the TouchKeys 25 kit for £330 (about US$500). Delivery is estimated for January 2014.

McPherson overviews the system in the pitch video below.

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