Model 260

Duophonic Pitch Class Generator Model 260

The Model 260 Duophonic Pitch Class Generator consists of two independent, voltage controlled pitch class generators. (A pitch class generator generates a particular pitch in every octave.) Frequency modulation inputs and a five band spectrum-shaping facility are provided.

When switched to the "barber pole" mode, an internal computer takes over pitch control of both generators, and issues pulses for triggering an external envelope generator (preferably a model 280, 281, or 284), which in turn drives a voltage controlled amplifier (a model 292 Lopass Gate is a good choice). When the 260's output signals are gated through the latter, Shepard tones and other auditory illusions (such as the tri-tone paradox) may be produced. The rate of change is variable to 2.5 octaves per second in either direction, and is voltage controllable. Additionally, the pitch intervals can be adjusted from quarter-tones to tri-tones.

With its multi-voicing, equalization, envelope shaping, and frequency modulation capabilities, you will find the 260 musically more interesting than the standard Shepard tone generator employed in perceptual psychology experiments.

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