the earliest musical installations known.
9 small DC motors provided with rubber wheels are attached to a steel
structure horizontally positioned and firmly clamped on a grand piano.
The little wheels brush lightly certain piano strings producing a series
of overtones proportional to the pressure imposed at a time to the string
on its various nodal points. The adjustment of the wheel to the string
is made by means of a micrometric screw (vernier). During the performance
motors are noiselessly displaceable along the beam to which they are attached,
so that other nodal points on different strings will be engaged.
After having set the nine motors on their respective positions on the
strings, the only player moves to a different area of the stage where
an analogue set of two tape/recorders in series (the first in record and
the second in play-back mode) is located. One of the two machines is voltage-controlled;
its speed can therefore be continuously varied, so that the resulting
feedback process does not only consist in an accumulation of the same
frequency but of a fluctuating wave of microtonal frequencies instead,
depending on the amount of speed-variation imposed.
The whole process consists in the alternation of sound-production and
sound-modification phases. It would end – ideally – when all attainable
positions on the strings are reached.