The ‘Mysterious Melody’ illusion was discovered and first published by Deutsch in Perception and Psychophysics, 19721. This musical brain teaser shows how our knowledge of a piece of music can have a profound influence on how we hear it. Suppose you play a well-known tune such that all the note names (C, D, E, and so on) are correct, but the tones are distributed haphazardly among three different octaves. If people are given no clues as to what the tune might be, they find it very difficult to identify. But once they know what to listen for, the melody becomes easy to follow.

The ‘Mysterious Melody’ illusion provides a striking example of ‘top-down processing’, or the use of previously acquired knowledge, in sound perception. Other examples occur in vision. For example, when you first view the picture below, all you see is a jumble of blobs. But when you are told that it is a spotted Dalmation dog against a dappled background, you begin to see its ears, nose, tail, and so on, until the entire outline of the dog emerges. Our stored knowledge of thousands of dogs that we have seen in the past enables us to reconstruct this image correctly. Analogously, once we are told the name of this ‘Mysterious Melody’ we can draw on our knowledge of what it normally sounds like, so that we can recognize it. 

      

This image initially appears as a jumble of blobs, but when we know what it represents we can see it correctly. Analogously, we can hear the ‘Mysterious Melody’ once we know its name.

Listen to the following example of a well-known tune, and try to guess its name.

sound example Deutsch's Mysterious Melody Sound Demonstration 1

The following example is identical to the first one, except that now the tones are all in the same octave. You should have no difficulty in recognizing this tune. Once you know what to listen for, listen to the pattern in Sound Demonstration 1 again - you might find it much easier to follow. If it is not obvious right away, listen a few more times and the tune should finally emerge.

speaker Deutsch's Mysterious Melody Sound Demonstration 2

References 2 – 4 provide further discussions of this illusion and its implications.

References:

1. Deutsch, D. Octave generalization and tune recognition. Perception & Psychophysics, 1972, 11, 411-412, [PDF Document]

2. Deutsch, D. The processing of pitch combinations In D. Deutsch (Ed.). The psychology of music, 3rd Edition, 2013, 249-325, San Diego: Elsevier. [PDF Document]

3. Deutsch, D. & Boulanger, R.C. Octave equivalence and the processing of tonal sequences. Music Perception, 1984, 2, 40-51, [PDF Document]

4. Deutsch, D. Octave generalization and the consolidation of melodic information. Canadian Journal of Psychology, 1979, 25, 399-405, [PDF Document]


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