Week 8: Grouping Mechanisms in Music - Deutsch

Helmholtz first introduced perception as “unconscious inference”.
Various mechanisms form linkages between objects (dimensions of frequency, amplitude, temporal, spatial & principles of Gestalt psychology) to group in conformity and enable us to interpret our environment visually and aurally.
1.First order elements – grouped together e.g. elements close together likely to belong to same object, similar sounds likely to originate from common source,
2.High order abstractions – perceptual synthesis

Perceptual grouping of single tones by:
1) Harmonicity e.g. musical instrument tones.
Perceptual separation or fusion
2) Onset synchronicity i.e. temporal factors
Also affects timbre. Two complex tones played together are perceptually more distinct when asynchronous than when played at the same time e.g. Bach used in polyphonic music
3) Auditory continuity e.g. “picket fence effect” alternated tone with a noise burst that was perceived as a continuous sounding tone.
Sudden amplitude drops between signals may destroy continuity effects
4) Frequency modulation enhances a vowel’s perceptual salience
5) Amplitude modulation
6) Ear of input

Perceptual grouping of sequences of tones:
Pitch proximity- links between tones close in pitch but separate tones that are far apart
Temporal proximity-pauses between notes are used as markers for grouping tones
Sound quality- different instruments playing together are linked by tones of similar timbre

Grouping multiple tone sequences in space (veridical or illusionary conjunction):
1) Scale illusions (Deutsch)
– perceptual reorganization (right-handers tend to hear higher tones on their right and lower tones on their left regardless of the direction they come - opposite of audience’s view of orchestral seating)
- Spatial reorganization e.g. Tchaikowsky Pathetique (Perception of musical passages is influenced by spatial arrangements of instruments)
Timbre differences aid in listener’s grouping into instrument type
Simultaneous sequences create grouping by pitch proximity when both ears receive simultaneous input.
Spatial grouping occurred when temporal disparities were presented by both ears
Glissando illusion
2) Octave illusions (Deutsch)
Hypothesized that octave illusions are result of a combination of pitch determining mechanism and spatial mechanism.

Melody perception from phase-shifted tones
Cause grouping by spatial location
Similar to octave illusions, melodic groupings are formed by the changing spatial positions of equal frequency tones.

Handedness correlates (both octave and scale illusions)
Octave illusions – right-handers hear high tone in right ear and low tone in left. This is maintained even when earphones positions is reversed
Left-handers vary in localization of where high and low tones sounds & what type of illusion

Treatise on music theory laws:
1. Stepwise progression
2. Crossing of voices in counterpart prohibited

In order for the listener to perceive sounds as intended by the composer, an understanding of basic perceptual phenomena is required. Perceptual effects occur when the laws are broken.