The Kickstarter campaign finished successfully on 2 September 2013. Thanks to all the project backers whose support made it possible!

TouchKeys

Capacitive Multi-Touch Sensing on a Physical Keyboard

Successfully funded on Kickstarter!


The TouchKeys are a new musical instrument transforming the piano-style keyboard into an expressive multi-touch control surface. The TouchKeys are touch sensors that can be added to the surface of any keyboard, measuring the location of the musician's fingers on the keys during performance.

We're launching this project on the crowd-funding website Kickstarter to raise funding to build sets of TouchKeys that any musician can install on their own keyboard. We'll also have a limited number of prebuilt instruments available. Your pledge on Kickstarter will get you a new set of TouchKeys from the first ever production run, shipping January 2014! Watch this page for updates!

TouchKeys in the News

Here's some of the recent press coverage of the TouchKeys:

About the TouchKeys

The TouchKeys project adds capacitive multi-touch sensing to the surface of any piano-style keyboard. Sensor overlays measure the location and contact area of the player's fingers on the key surfaces, and the data can be used to create a wide range of expressive effects including vibrato, pitch bends, timbre changes and improved emulations of non-keyboard instruments. The keyboard is traditionally a discrete interface, measuring notes by onset and release. The TouchKeys let the player continuously shape each note through the subtle expressive details of their finger motion.

Features

The TouchKeys are sensor overlays that attach to any standard-size keyboard, acoustic or electronic. Each key uses capacitive touch sensing to precisely locate one or more fingers on the key surface. Here are a few of the main features:

  • High-resolution position measurement with over 1500 points of resolution in the long axis, 256 points in the narrow axis. That's sub-millimeter accuracy!
  • XY position on every key, including the black keys. (The narrow part of the white keys senses on the long axis only.)
  • Contact area measurement distinguishes the tip and the pad of the finger, and can indicate finger pressure in some circumstances.
  • Up to 3 touches per key allows new multi-finger techniques on the keyboard.
  • 200Hz sample rate makes for a natural, low-latency interaction.
  • Configurable keyboard size: the sensors can install on anything from a 2-octave portable keyboard to a 97-key Boesendorfer Imperial Grand piano. Choose the keyboard with the action and features you want.
  • OSC and MIDI support for a wide range of mappings from touch data to sound.

How It Works

Simulation of touch location calculation in a single axis

The sensors work by measuring the capacitance of a collection of small conductive pads on the surface. Touching the key causes several adjacent pads to increase in capacitance. A microcontroller on the key interpolates between the values to arrive at a precise estimate of the contact location. Contact area can be sensed by observing the overall magnitude of change in capacitance.

Once each key has calculated its touch information, another microcontroller collects the data from every key and transmits it to a computer by USB. Software on the computer side generates OSC and MIDI messages that can be used by a wide variety of synthesis software. The software also uses the MIDI data from the underlying keyboard to produce a complete picture of the performer's actions.

More information on the design and operation of the TouchKeys can be found in the papers below:

Selected References

  1. A. McPherson and Y. Kim. Design and applications of a multi-touch musical keyboard. Proc. Sound and Music Computing, Padova, Italy, 2011. PDF
  2. A. McPherson. TouchKeys: capacitive multi-touch sensing on a physical keyboard. Proc. New Interfaces for Musical Expression, Ann Arbor, MI, USA, 2012. PDF
  3. C. Heinrichs and A. McPherson. A hybrid keyboard-guitar interface using capacitive touch sensing and physical modeling. Proc. Sound and Music Computing, Copenhagen, Denmark, 2012. PDF | Video Demo
  4. A. McPherson, A. Gierakowski and A. Stark. The space between the notes: adding expressive pitch control to the piano keyboard. Proc. ACM Conference on Human Factors in Computing Systems (CHI), Paris, France, 2013. PDF | Link

More Videos

The TouchKeys project reflects 2 years of development at Drexel University and Queen Mary, University of London. These videos from current and earlier generations of the instrument show some of its other capabilities:


TouchKeys electric piano improvisations


Polyphonic aftertouch and the CS-80


TouchKeys techniques: vibrato and pitch bends


Introduction to TouchKeys hardware (original design from 2011).


Physically-modelled guitar controlled from the TouchKeys generation 2, early 2012. (Christian Heinrichs and Andrew McPherson).