On the Role of Ambiguity of Perceived Pitch in Music

Ambiguity, and its resolution, are key elements of communication; and, in particular, of music (See, e.g., the examples discussed by L. Bernstein in bis f amous Harvard lectures [1). Besides rhythmical ambiguity, it is particularly harmonic ambiguity of both simultaneaus notes, i.e., chords, and of sequential notes, i.e., rnelodies, that play a major role. Auditory pitch comes into play through the intimate relationship that was discovered to exist between pitch (in the term's generat psychophysical sense), and musical harmony. What in music theory is called a root, in psychophysical terms is a certain type of pitch, i.e., virtual pitch [6, 71 Ambiguity of root (i.e., harmony) is synonymaus with ambiguity of virtual pitch. Those relationships are dependent on the ide~ that auditory pitch exists on various Ievels of the perceptual hierarchy. On the lowest, i.e., primary Ievel, pitch exists as an aural representation of part-tone frequency, i.e., spectral pitch; spectral pitch can be regarded as analogaus to primary visual contour [81. On a higher Ievel, a set (i.e., two or more) of spectral pitches ordinarily create virtual pitches; the latter are analogaus to "illusory contours" in vision. As was demonstrated by Hall and Peters [31, under certain conditions even non-simultaneaus spectral pitches can create virtual pitches. The present paper is going to briefly discu.ss the following notions; • Ambiguity of pitch is ordinary and gradual; • ambiguity of pitch is confined to a finite set of alternatives; • ambiguity of pitch creates perceptual similarity of sound objects; • similarity in turn is a basic organisational principle of music.