The player Theremin got a little press a coupla Digests ago, and I'd like
to offer a bit more about it.

Jason Barile, web master of the Theremin home page, is a grad student in
the Intelligent Robotics Lab here at Vanderbilt University.  This group
has done some amazing stuff, and the player Theremin is no exception.

The key challenge is that playing a Theremin is critically dependent on
auditory feedback, since there is not even a fingerboard for pitch
reference, such as found in a violin.  Clara Rockmore (arguably the most
skilled Thereminist ever) insisted on having her monitor loudspeaker
placed quite exactly with reference to where she stood.  The bottom line
is that the pitch sensitivity of the instrument is such that one cannot
simply pre-program certain positions of the robot arm for certain notes.
If the placement of the antenna is off by more than a couple of
millimeters, it will sound horrible (eyewitness account).

What Jason did was to use a standard keyboard for pitch reference.  The
keyboard creates a note which is sent to a digital sampler.  The Theremin
(a Moog "Big Briar" unit, incidentally) also sends its output to the
sampler.  In both cases, the zero-crossings of the waveforms are
calculated.  A computer program that acts much like a phase-locked loop
then moves the robot arm until the zero-crossings are synchronized.  As a
consequence, the system has a fair amount of ... er, portamento.  The
robot arm itself has a fair amount of mass.  When Jason tried to speed up
the response of the arm to minimize the glissando, the system became
unstable.

Voila!  Vibrato! (Could you say serendipity?)  The vibrato is in fact
very impressive and sounds quite like that from a human player, although
there is some detraction because of all the rattling in the hardware of
the robot arm.

I must candidly admit that the last time I saw the player Theremin
perform, it was not quite a self-playing unit.  The requisite reference
notes were input manually via the keyboard.  Since the keyboard is a MIDI
device, one would like to think that total automation is just around the
corner.  I believe that, given the sophistication of the computer support
and robot control mechanisms, this thing even outdoes a Violano Virtuoso
in terms of complexity.  The irony is that it was fiddled together (so to
speak) over a couple of weekends.

A. B. Bonds

 [ Editor's Exaltation:
 [
 [ Wowie!  A Midi-controlled Player Theremin !!  This is BIG news --
 [ maybe it's even the first DIFFERENT mechanical music device in many
 [ decades!  How can we get photographs for the MMD web site?
 [
 [ Robbie