This is a quick, non-musical demo of the Therething, an open source MIDI theremin thing:
Ultrasonic sensors are used to return a distance value, from the sensor to the player’s hand. This value is converted by an Arduino or other microcontroller into a MIDI key value and is output at the correct baud rate (31,250 bps) onto a serial pin. Since MIDI needs a signal to turn off a key pitch as well as a signal to turn it on, two MIDI signals are sent – one to turn off the previous note and one to activate the required note. The new note-on message is sent BEFORE the previous note is turned off. This is to allow for a slide/portamento effect, making it sound more theremin-like on certain synths.
Volume is controlled using a similar approach, using an ultrasonic transducer that is pointing away from the note-generating sensor (to avoid cross-talk or interference).
See the BuildBrighton site for construction details.
A quick demo of the new firmware for the midi theremin designed by the BuildBrighton hackerspace. See http://www.buildbrighton.com/wiki/Theremin for details.
Uses ultrasonic sensors hooked up to an arduino microcontroller. The arduino outputs MIDI which is then fed in to Ableton Live with an Operator synth set up.