Up-Down Melody cycles

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This example is a short up-down melody. The auditory event produced by an isolated tone from a single instrument is dominated by a static auditory figure that appears out of the floor of auditory space as the tone comes on, and remains fixed in position for as long as the tone is sustained. At the end of the tone, the figure just decays rapidly back into the floor of the space without changing position. Isolated musical tones are some of the simplest auditory events in everyday life. When an instrument plays a melody, the information concerning instrument family is fixed and the information concerning instrument register is fixed. The melody information is conveyed by the sequence of pulse rates in the notes; the melody is actually the sequence of pulse-rate ratios between successive notes. A melody can be regarded as a compound auditory event, although many melodies remain relatively simple conceptually. The example (below) shows the compound auditory event produced by a seven note melody (do, re, mi, so, mi, re, do). The "instrument" in this case is just a click train -- a pulse-resonance sound without resonances. It is a useful instrument because it excites all channels of the auditory image and produces a canonical auditory figure. In the example, the auditory figures associated with each note appear and disappear very rapidly, so the figures shift back and forth in discrete steps as the melody proceeds. In this example, it is only the rate of the clicks in the train that is changing, and as a result, the motion in the image is predominantly horizontal. This is the characteristic of pulse rate information in the auditory image; it determines the position of the set of auditory figures in the auditory image, and it determines the pitch of the tone. Pulse rate is the property that is normally varied in music to produce the melody, and it is the only information in this auditory event, beyond the fact that the instrument is a computer producing clicks in a regular train.

A simple up-down melody as an example of a compound auditory event

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Between notes the figures associated with the tone that just ended decay as a unit into the floor of the space and the figures associated with the next tone rise out of the floor into position. During each note, there are about 50 cycles of the sound, that is, 40 clicks spaced by periods of about 8 ms. This gives some impression of the speed of auditory processing, and the role of temporal integration; the cycles of the sound are entering the ear and proceeding through the auditory system at a rate in excess of 100 per second, but the melody is dominated by a sequence of static, high-resolution, auditory figures.

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