The ingredients of melody
Fig. 4 Perceived musical sequences in each ear (Deutsch, 1999)
The unique thing about melodies is that, while being made up of individual tones of varying pitches and durations, they are somehow perceived and experienced as a coherent whole. To begin the investigation of melody perception, the authors first identify the essential components of melody, including pitch, interval, contour, harmony, and key.
Pitch
We've covered pitch in chapters 2 and 3, where it is closely related to the frequency of a pure tone or the fundamental frequency of a complex sound wave. This provides us with one way to distinguish between pitches, that is, using pitch heights (i.e., related to the frequency of vibration). Because the note C4 has a greater fundamental frequency than that of C3, it has a higher pitch height and is hence a different pitch.
Another way to categorise pitches is using chroma, which refers to the category or class that different pitches might belong to. This categorisation is completely arbitrary, but for the sake of simplicity, we are going to adopt chroma categories of Western music, which group all the notes on a piano onto 12 different pitch chromas (i.e., note names like C, D, F#, Ab, etc). Here, while C3 and C4 might have different pitch heights, because they belong to the same chroma categories, they can be identified within the same note class.
Interval
Intervals refer to the pitch gap between one pitch and the next. This is an important part of melody perception because of transposition. To transpose a melody is simply to begin the original melody on a different note, yet keep the relationship from one note to the next exactly the same. The authors use the tune "Over the rainbow" as an example -- the original melody can be transposed from one key to another (e.g., C-C'-B-G-A-B-C' to D-D'-C#-A-B-C#-D'), yet still be perceived as having the same melody. While pitch height and chroma change, the intervallic relationship between pitches remains invariant.
Contour
Melodic contour refers to how the melody rises and falls with each successive pitch. More generally, it is reflected by the shape of the melodic line. Melodic contours are usually studied in relation to changes in melodic direction, as these changes reflect salient and easily perceived points of the melody. For instance, performance errors are far more noticeable when they disrupt the original melodic contour, while infants have been observed to distinguish between melodies if a different pitch changes the shape of the melody (Trehub et al., 1984).
Harmony
It might seem strange to see harmony listed as a component of melody. After all, harmony implies the simultaneous playing of pitches, whereas melody refers more to discrete pitches played in a sequence. Here, Tan and colleagues argue that the harmony underlying the melody can influence the perception of the latter. For instance, different segments of a melody might be perceived based on the harmonic structure implied, such as when an authentic cadence is used (i.e., a music progression going from the dominant to the tonic chord is used). Furthermore, melody can imply harmony, such as in bebop jazz, where melodic lines often 'spell out' the harmony by emphasising notes that define the chord.
Key
Finally, key refers to the type of musical scale implied by the melody. Using the Western diatonic system as an example, melodies might be tonal or atonal. Tonal melodies suggest that the music is played within a specific key context, such as a major or minor key. Meanwhile, atonal melodies do not imply any key and might sound quite chilling or jarring for the uninitiated.
Another important thing to note here is that the key in which the melody is played places constraints on which notes sound consonant. For instance, while there are 12 pitch chromas, a major key limits the number of 'acceptable' notes to 7. Notes outside of these 7 often result in highly salient and dissonant sounds, and might even be used intentionally to add tension to the music.
The perceptual organisation of melodies
Gestalt principles of perception
As mentioned earlier, melodies are interesting in that they are perceived as a higher-order whole that seems to transcend their lower-order constituent parts. To explain how this might work, Tan and colleagues turn to Gestalt psychology, which studies how individual components come to be processed and understood as an organised, structured whole. Most of the early work applied to vision, yielding Gestalt principles (see Fig. 1) such as: Proximity (where components near each other tend to be perceived together), Similarity (where similar elements are perceived as a group, especially in the presence of more than one kind of element), Closure (the tendency to perceive an incomplete pattern as a whole), and Continuity (the tendency to perceive organise elements into smooth continuous patterns, instead of ones with abrupt changes in direction).
Fig. 1 Examples of Gestalt principles (Tan et al., 2010)
Applying Gestalt principles to music
Applying the principle of proximity to music explains why melodies typically contain successive pitches that are in close proximity to each other. Indeed, a melody might become more difficult to perceive if constituent pitches are separated by larger intervals, rests (i.e., breaks in time), or are played from drastically different spatial locations. Empirically, Deutsch (1995) found that when familiar melodies were replaced with octave-scrambled ones (i.e., each note was randomly displaced to another octave), participants found it challenging to recognise those melodies. Not only that, participants often did not even consider these octave-scrambled sequences as melodies!
Meanwhile, Dowling (1973) interleaved 2 melodies (see Fig. 2) and found that listeners could only discriminate between the melodies when they were played in different pitch ranges. This is likely because notes within each melody were played in close proximity to each other, while notes between melodies were 'far' away in terms of pitch, hence allowing participants to more easily separate the 2 interleaved melodies.
Fig. 2 A visual analogy of interleaving (Tan et al., 2010)
Next, applying the principle of similarity explains how individuals might be able to distinguish the separate melodies played simultaneously, such as in a band or orchestra. Here, each instrument produces a unique sound quality or timbre, which serves as a point of similarity that listeners can latch on to. Similarity can also manifest in the form of the repetition of musical themes, motifs and patterns throughout the music, which can add a sense of unity and coherence to the music as a whole
Finally, the principle of closure might explain why ending melodies on the tonic (i.e., the first note of the scale, usually associated with stability) provides a feeling of finality, and also how leading tones and dominant chords set up strong feelings of anticipation that can only be resolved by the tonic. DeWitt & Samuel (1990) describe this in their study of perceptual restoration, where they played a scale with one tone either present or replaced with noise. Generally, if participants expected the distorted tone to complete the scale, they had a harder time determining if it was present or not than if the distorted tone was not expected to complete the scale. Moreover, participants were more likely to perceive the missing pitch if the number of tones played beforehand was increased, suggesting that providing more context increases the power of the principle of closure in pitch perception.
The scale illusion
Gestalt principles have also been used to explain auditory illusions. For example, we can turn to the scale illusion, which was demonstrated by Deutsch (1975). Here, participants listened to 2 musical sequences simultaneously, with one sequence fed to the left ear and the other to the right. These 2 sequences were C major scales played either in ascending or descending fashion, and were also played in an alternating manner (see Fig. 3). After listening, participants were asked to reproduce what they heard in each ear. Astonishingly, while the true nature of both sequences was highly jagged, many reported hearing smooth melodic contours in both ears. Specifically, the scale descended before ascending in the right ear, and ascended before descending in the left ear (see Fig. 4).
Fig. 3 Original musical sequences presented in each ear (Deutsch, 1999)
The results above can be explained by the principles of proximity, similarity, and closure. For instance, the tones played were in similar pitch ranges (proximity), with similar timbres (similarity), and contextualised in a musical sequence that strongly implies a familiar scale (closure). On the other hand, the authors point out how the results contradict the principle of continuity -- for this to be observed, participants should report hearing melodic contours that simply ascend or descend, and not contours with a directional change in between!
Concluding remarks
This concludes the first part of Chapter 5. In the following post, we'll continue the discussion on the role of memory in perceiving pitch and melody, and also look at some neuroscientific evidence for music perception!
References
Deutsch, D. (1995). Musical illusions and paradoxes. http://ci.nii.ac.jp/ncid/BA42044822
Deutsch, D. (1999). Grouping mechanisms in music. In Elsevier eBooks (pp. 299–348). https://doi.org/10.1016/b978-012213564-4/50010-x
Dowling, W. (1973). The perception of interleaved melodies. Cognitive Psychology, 5(3), 322–337. https://doi.org/10.1016/0010-0285(73)90040-6
Tan, S., Pfordresher, P., & Harré, R. (2010). Psychology of Music: From Sound to Significance. http://ci.nii.ac.jp/ncid/BB01824497
Trehub, S. E., Bull, D., & Thorpe, L. A. (1984). Infants’ perception of melodies: The role of Melodic Contour. Child Development, 55(3), 821. https://doi.org/10.2307/1130133
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