As is clear from common experience in listening to melodies, sequences of
tones can form coherent wholes in the perception. There are, however, tone
sequences in which the successive tones are not perceived as coherent. This
phenomenon we call fission. Since fission is not a generally known effect,
examples of it and its counterpart temporal coherence are the subject of the
examples that follow.
There are numerous possible ways of composing tone sequences that are not perceived as coherent.
Fission can be observed in tone sequences in which the successive tones differ too much in frequency,
spectrum, amplitude and so on.
But a characteristic of these phenomena is that
the occurrence of a certain percept does not depend only on these objective features.
There are large intermediate ranges of these features in which
the observer himself can influence his percepts.
It follows that it is sometimes difficult to make the demonstrations unambiguous.
The listener is therefore encouraged to listen in as many ways as he can.
The successive parts of this set of circuits are intended to illustrate
various aspects of temporal coherence and fission. They generally run
parallel to the chapters of the thesis "Temporal Coherence in the Perception
of Tone Sequences".
Most of the circuits are relatively simple configurations of oscillators
and sequencers that play patterns of tones.
You may be asked to adjust parameters such as tone repetition time,
relative frequency, amplitude and so on. The controls for these parameters
will be labeled with names such as 'T slider', 'tone A frequency' etc.
In order to avoid the influence of non-linear distortion in equipment and
the human ear it is recommended to listen to the circuits at a moderate
sound level of about 40 dB above the normal hearing threshold.