Perception

In perception of sound, listeners group complex auditory information into meaningful structures. Empirical research has explored how listeners perceive these sound signals and their sources as building blocks of music, including melody, meter and rhythm, pitch, tonality, and harmony.

A listener perceives a melody when a sequence of pitches are grouped together to form a musical phrase. The appearance of two successive pitches implies a third, and this implication can be completely realized, partially realized, or denied. The core of this implication-realization model is that sameness/similarity implies more sameness/similarity, and differentiation implies more differentiation. Parameters involved include interval size (pitch space between two tones) and registral direction (up, down, or sideways). For example, a listener most expects an ascending F-G-A to continue in the same direction because F-G and G-A are both the same ascending intervals.

A melody has essential notes for perceiving the melodic pattern. However, it may also have ornamental notes that can be removed to create a simplified version of the same melody. When judging similarity between two melodies, listeners make more errors perceiving intervals than the rise or fall of the melodic line, the contour. Changes in contour, a salient part of melody perception, attract listeners' attention. In a melody where notes go up-up-up-up-down-down, the fifth note draws attention. Listeners have more difficulty processing “complicated” melodies with more contour changes than “simpler” melodies that do not.

Often, listeners do not hear melodies in isolation, but part of a mass of auditory information. Auditory scene analysis, the extraction of musical patterns from outward cacophony, occurs every time a person distinguishes the flute line from the cellos. Listeners assign auditory information to one stream, an inferred auditory source, or another. To research auditory scene analysis, scholars use melodic interleaving: notes from one melody alternate with the notes of another (melody 1: A-B-C, melody 2: D-E-F, interleaved melody: A-D-B-E-C-F).

When two interleaved melodies share similar pitch ranges, listeners often perceive one auditory stream. If they occur in different pitch ranges, a listener hears two distinct auditory streams. A musical line that alternates between high and low registers suggests two melodic lines, despite only one instrument's presence (e.g., Johann Sebastian Bach solo cello suites).

One melody perceived as multiple lines often implies harmony, a sequence of chords. However, the perception of implied harmony depends upon the listener's musical skill. When rating similarity between multiple melodies, both musicians and nonmusicians used contour; yet, only musicians also used implied harmony.