Active Control of a Vibrating String

Edgar Berdahl

Websites for related conference papers:

Some stringed instruments that I modified/made for the project:

Alpha version: practice installing piezoelectric sensors

Beta version: configuration allowing collocated control of horizontal and vertical axes

Version 1.0: can be used for performances

Sample sounds produced using version one, which has only one string:

For each example, an effect from the Eventide Orville was placed in the feedback loop. A dynamic range limiter was used to induce stability, and the loop gain was adjusted by hand to control the intensity of the feedback. Only one axis is being actuated, but both the horizontal and vertical axes are being sensed.

The effect produces a series of arpeggiated notes based on what it guesses is the fundamental.
The effect outputs "clouds" of tonal sound related to the fundamental frequency.
This effect causes modulations much like that of a Leslie organ.
This example demonstrates vibrato with some additional distortion.
The effect delays the signal by about 1/4sec and shifts the pitch up by a fourth. Note that the guitar only has one string.
This effect plays a scale up from what it guesses is the fundamental frequency.

To Edgar Berdahl's Web Page

To Julius O. Smith III's Web Page