Pitch and Timbre II

1
Pitch and Timbre II

• categorisation, recognition and scale structures

2
Concepts

• Recognition
• What is it?
• Have I heard it before?
• Categorisation
• Division of continuous parameter (e.g. pitch)
  into discrete categories
• Scale
• What properties do scales have?
• How are these relevant to perception?

3
Recognition of Timbres 1

• Two main theories
• Information Processing
• analysis
• matching
• association
• Ecological Perception
• direct response to invariants
• McAdams, S. (1993). Recognition of sound sources
  and events. In S. McAdams and E. Bigand (eds.)
  Thinking in sound the cognitive psychology of
  human audition. Oxford University Press.

4
Recognition of Timbres 2

• Problem
• Perceptual constancy physically different sounds
  specify the same object for us
• Solutions?
• Prototype Theory (how close to an ideal?)
• Feature Matching (bundles of features for each
  source to be recognised)
• Perception of higher-order variables (e.g.
  time)
• Innate systems (such as for speech?)
• Handel, S. (1989). Listening an introduction to
  the perception of auditory events. Cambridge,
  Mass. London MIT Press.

5
Categorisation of Pitch

• Pitch exists on a continuum
• We hear discrete pitches and tuning
• Semitones are the lowest level of consistent
  discrete perception (identification and
  discrimination) for trained westerners
• What about other cultures and musical systems?
• Relationship with scales

6
Scales (and categorisation)

• Perceptual constraints
• limit on number of elements
• types of structure to help us encode long
  sequences
• What kinds of structure are there in scales?
• Octave equivalence
• Coherence (we cant confuse a single step with a
  leap)
• Completeness (all possible intervals richness)
• Unequal steps (help us to navigate)

7
Octave Equivalence

• C1 is the same as C2
• Scale repeats its interval structure at octave
• 12 14 16 17
• Semitones 0 2 4 5 7 9 11 0 2 4 5
• Note Names C D E F G A B C D E F

8
Coherence

• 12 14 16 17
• Semitones 0 2 4 5 7 9 11 0 2 4 5
• Note Names C D E F G A B C D E F
• How many different intervals are there between
  consecutive scale members in the major scale?
• Are these intervals smaller, the same size or
  larger than the intervals between non-consecutive
  scale members?
• Is this property true of all scales?

9
Coherence II

• Harmonic Minor scale
• 0 2 3 5 7 8 11 0 2
• How many different intervals are there between
  consecutive notes?
• Are these intervals smaller, the same size or
  larger than the intervals between non-consecutive
  scale members?

10
Completeness

• 0 2 4 5 7 9 11 0
• 0 2 3 5 7 8 11 0
• How many intervals can you construct from the
  minor and major scales above?
• Other scales?

11
Unequal steps (and Uniqueness)

• Why might the chromatic and whole-tone scales be
  a problem for our navigation?
• 0 1 2 3 4 5 6 7 8 9 10 11 0
• 0 2 4 6 8 10 0
• 0 2 4 5 7 9 11 0 2

12
Summary

• Pitch and timbre are perceived categorically
• Perceptual constancy causes problems for timbre
  recognition
• Many competing theories of timbre recognition
• In western music (and elsewhere) scales provide
  useful clues for perception