An Exploration of timbre: its perception, analysis and representation Dr. Deirdre Bolger CNRS-LMS,Paris Invited lecture, Institut für Musikwissenschaft, Universität Graz, Austria, 23 November 2005

Timbre is… “…the quality of sound that is not loudness and pitch.” (American Standards Association) Distinguishes different musical instruments playing the same note. Separate from frequency, amplitude and duration while existing due their interaction. A quality that differentiates one complex sound from another of identical pitch and loudness.

Timbre is… A quality of sound that is… based on the physical characteristics of the sound. a perceptual phenomenon resulting from the action of listening. Musical point of view: how is this quality of sound considered? …

Perceptual significance of timbre The most important and relevant feature of auditory events. Acute memory for timbral qualities (Schellenberg et al, 1999). Distinguishing of timbres in everyday life. Absolute pitch perception. Auditory streaming.

Timbre in music: Two descriptions (Hadja et al, 1994): Categorical: Identification of the sound source, the musical instrument. Ordinal: Ordering of sounds on perceptual dimensions. Correspondence to scales of physical measurements. In music, timbre is can be investigated at two levels: Categorical level: instruments and combination their combination Within instruments: variations in playing style and technique.

Ordinal description of timbre Pitch  frequency scale Dynamics  energy scale Rhythm  relative duration (time) Timbre  …spectral and temporal aspects of sound… Many ways of measuring timbre. Therefore… Timbre is described as multidimensional.

Spectral and temporal envelopes of sound: Example-oboe A4 Spectral envelopeTemporal envelope

Spectral and temporal descriptions of timbre Spectral descriptions of timbre: frequency and energy of spectral envelope. Temporal descriptions of timbre: evolution of the energy of the spectrum over time. Spectral descriptions  sustained sounds. Temporal descriptions  impulsive sounds, speech

NameTypePhysical Correlate Perceptual Correlate Description Spectral centroid SpectralEnergy concentration in low/high spectral area Brightness/ Dullness Balance of energy in spectrum. IrregularitySpectralFluctuating energy between adjacent partials RichnessAmplitude variation of adjacent components. RoughnessSpectralBeating of overlapping partials Harshness/ Smoothness Inharmonic and noise components in spectrum. HarmonicitySpectralHarmonic/ Inharmonic Cohesive/ Diffuse Ratio of harmonic to inharmonic spectral components. Attack/ Decay times TemporalSlope of attack and decay Instrument identification Time taken to reach max. amp from 0 (attack).

Spectral and temporal analysis: Example-piano B4

Spectral timbre analysis: Piano B4

Spectral timbral analysis: Oboe B4

The quest for a timbre structure Questions posed relating to: Timbre hierarchy (Lerdahl, 1987). Timbre-based musical form (McAdams and Cunibile, 1992). Why such questions? Timbre as a compositional tool. Signal processing techniques  detailed manipulation of timbre. Perceptually very interesting: How do we perceive relations between timbres? Is it possible to perceive timbre hierarchically?

A timbre structure: Requirements Hierarchical arrangement of timbres that is perceived as such. this implies the need for… A type of timbre scale based on certain defined timbre relations or… Timbre intervals!

Perceiving timbre relations: Timbre intervals A movement within a n- dimensional space. A “..vector in space connecting two timbres..” (McAdams, 1999) with a certain orientation and length. Research by McAdams and Cunibile (1992) to test the perception of timbre intervals.

Theory of timbral hierarchies (Lerdahl, 1987): Properties Main interest: a timbre hierarchy as a tool for musical composition. Uses synthesised timbres  not derived from existing timbre relations. Creating timbre scales: Consonant/dissonant timbre relations. Stability/instability of timbre relations. Implemented a hierarchy for a 2D timbre space.

Theory of timbral hierarchies: timbre relations Consonance/dissonance relations: Consonant-dissonant movement  relaxation Dissonant-consonant movement  tension. Continuum of timbral stability: Ordering of timbres. Relative consonance/dissonance of timbre events. Examples Increasing roughness  increasing instability. Increasing brightness  increasing instability. Definition of prototype  most stable timbre event. Increasing distance from prototype  increasing dissonance. Perceptual relevance or hierarchy.

Theory of timbral hierarchies: Examples The prototypes for each dimension are highlighted  h0v2 root Taken from Lerdahl (1987; p148)

Theory of timbral hierarchies: Reflections on music analysis Formal pitch structure  the creation and analysis of music. But… The timbre hierarchy  musical creation. Why… Complete control over sound material, not possible in analysis. a timbre space: an instrument a particular musician of a certain level a certain environment Definition of a prototype for musical analysis  problematic

Timbre analysis: other issues Timbre based on spectrum? Timbre based in perception? Timbre as property of sound spectrum. Timbre as a product of culture Timbre in culture  implications for timbre perception.