Scale, key, and contour in the discrimination of tuned and mistuned approximations to melody

Abstract

Approximations to melody were synthesized using a computational technique whereby the occurrences of certain notes and intervals were made more probable than others. In experimental melodies, these notes and intervals were chosen to clarify the diatonic scale and the key of the melody. To clarify the scale of a melody, the probabilities of the diatonic scale notes were made higher than those of nonscale notes. Perception of these melodies was compared with control melodies in which the higher probabilities were assigned to a different set of notes. The latter were chosen so that no single diatonic scale embraced the set. To clarify the key of a melody, intervals with a low "fifth-span" were made more probable than intervals with a high fifth-span, while control melodies had the higher probabilities assigned to intervals with a high fifth-span. Here fifth-span is the separation of two notes measured along a progression of fifths. Listeners heard pairs of melodies and were asked to discriminate between pairs of different melodies and pairs in which the second melody was an exact transposition of the first. It was found that this discrimination was easier if the first melody contained a high proportion of diatonic-scale notes. A similar perceptual advantage held for melodies composed of intervals with low fifth-spans. Discrimination was also easier if the contour of the second melody in a different-pair differed from that of the first. The melodies were then mistuned by changing the size of the quantal interval (semitone) by a constant (log)factor. In this way, two types ofmistuned melodies were generated: melodies for which the quantal interval was reduced, and melodies for which the quantal interval was increased. Discrimination advantages for diatonic scale and low filth-span were not found for these mistuned melodies. Nevertheless, differences in contour still led to improved discrimination. It is concluded that melody perception draws on music-specific perceptual knowledge as well as more general factors. Mistuning destroys the perceptual advantages found for the melodies with a clear scale and a clear key. These attributes are therefore considered to be specific to music. By contrast, the perceptual salience of pitch contours is more general in origin, because it was shown for both the tuned and the mistuned tone sequences. This paper is concerned with the effects that "rnistuning" might have on the perceptual discrimination of melody pairs. For "tuned" melodies the note frequencies are based on the values of 12-tone equal temperament. This is a 12-fold division of the 2: 1 frequency ratio of the octave, forming logarithmically equal semitones. Since all other intervals are integer multiples of the semitone, it may be thought of as the "quanta! interval." For •'rnistuned' melodies, this set of note frequencies is either expanded or compressed. This is done by increasing or decreasing the size of the quanta! interval by a constant (log) amount. Physical discrepancies between melody pairs are therefore proporti...

Tonal strength and melody recognition after long and short delays

“…Stimuli with lower tonal strength should have less similarity of tonality and thus should generate less confusion. Finally, the weaker the tonality, the less well remembered should be the melody, which agrees with Cuddy et al (1981) and Watkins (1985). Even contour should be less well remembered for the atonal melodies, in keeping with Bartlett and Dowling's (1988) result that contour changes were more difficult to recognize in atonal (vs. tonal) test melodies.…”

Contributions of pitch contour, tonality, rhythm, and meter to melodic similarity.

“…The order effects show that participants seem to have had greater trouble differentiating between sequences when the first sequence was a variant that departed more from the original (as in Bartlett & Dowling, 1988;Watkins, 1985). This pattern is especially notable in Figure 10, which depicts the main effects of comparing each time level manipulation.…”

Effects of length, tonal structure, and contour in the recognition of tone series

“…A useful way of controlling nonmusical artifacts is provided by Watkins (1985), who used series of tones with either tuned or mistuned melodic intervals to separate effects due to music-perceptual knowledge from more gen-RECOGNITION OF TONE SERIES 629 eral perceptual factors. "Tuned" tone series contain note frequencies based on the 12-tone equal temperamentthat is, the octave is divided into 12 equal semitones (the smallest interval) by the twelvefold division of the 2: 1 ratio of the octave.…”

“…Mistuning as used by Watkins (1985) and in the present Experiments 3 and 4 can be explained as follows. The constant frequency ratio that relates the notes of adjacent semitones (called quantal intervals by Watkins, 1985) within equal-temperament tuning, can be described with the formula…”