Taxonomy of Orchestral Effects Related to Auditory Grouping
This page introduces the Taxonomy of Orchestral Effects Related to Auditory Grouping. The first section provides background to the theory. The next section explains the Auditory Grouping Processes. The following section presents the Taxonomic Categories: Concurrent Grouping, Sequential Grouping, and Segmental Grouping.
For an in-depth article, please visit Music Theory Online
Background
Orchestration is known as the art of combining instruments through various techniques to achieve a particular sonic goal. However, the practice of orchestration has not been studied systematically with the aim of developing a theory of the conditions under which certain orchestration techniques work, and how they are perceived.
The aim of the Orchestration and Perception Project, and now various sub-axes of ACTOR’s Analysis Axis, is to develop a psychological foundation for a theory of orchestration practice based on perceptual principles associated with musical timbre. In this ongoing research program, we are studying implicit theory contained within orchestration treatises and orchestral scores.
We discovered that many orchestration aims are related to auditory grouping processes (McAdams & Bregman, 1979), which organize the acoustic environment and determine what sounds are grouped together into musical events in concurrent grouping, whether these events are connected into musical streams in sequential grouping, and how listeners chunk event streams into musical units such as motifs, phrases, or themes in segmental grouping (as shown in Figure 1 from McAdams, Goodchild, and Soden - in preparation).
![Auditory grouping processes and the resulting perceptual qualities and orchestral effects. [Reproduced from Goodchild and McAdams, 2018, Fig. 1]](https://images.squarespace-cdn.com/content/v1/60808497d3ad1e29c346fe97/1619205026043-CAYKZZNNDZYA2TD7P0PF/image-asset.png)
Auditory grouping processes and the resulting perceptual qualities and orchestral effects. [Reproduced from Goodchild and McAdams, 2018, Fig. 1]
Orchestral grouping effects and auditory grouping processes
Timbre emerges from the perceptual fusion of acoustical components into a single auditory event in concurrent grouping. According to Sandell (1995), the results of instrumental combinations include two types of blend: timbral augmentation (dominant instrument is embellished by subservient instruments) and timbral emergence (synthesizing a new timbre that is identified as none of its constituent instruments). Timbral heterogeneity results when sounds are not blended and separately identifiable.
In sequential grouping, timbre is also involved in auditory stream integration, and involves the perceptual connecting of a succession of similar events and the separation of events with different perceptual qualities into distinct groups: integration of events into a melodic stream or surface texture, and segregation of events into different streams based on timbral differences that may signal multiple sound sources or stratification of musical material into different foreground and background layers of more or less prominence. The events are either stable - played by the same instruments or groups of instruments - or transforming - where the instrumentation changes over the duration of the passage.
Timbre is also implicated in segmental grouping. Discontinuities promote chunking of musical units, called timbral contrasts with varying orchestration (e.g., antiphonal contrasts, timbral echoes). Timbral progression occurs over longer timespans, and can be used to create coherence and dramatic shape within larger-scale formal units.
The information provides an overview of the orchestral effect categories based on the grouping processes involved. Each description contains a link to a representative example, which contains a detailed view of the annotation, a view of the score, and a sound clip
Taxonomic categories and grouping processes
1. Concurrent Grouping
Definition: Concurrent grouping concerns the integration or separation of simultaneously present acoustic information from multiple sound sources. This process is responsible for auditory event formation. In orchestration an "event" can therefore be formed from several grouped sound sources.
Perceptual fusion results in the formation of auditory events.
Event formation depends on concurrent grouping principles:
Onset (and offset) synchrony
Harmonicity
Parallel changes in amplitude and frequency
But fusion of multiple sound sources also depends on spectral relations
Overlap in frequency spectra of constituent events
Overall spectral density
Auditory attributes (pitch, timbre, etc.) are computed from event properties, i.e. grouping precedes attribute extraction
Therefore, timbre depends on concurrent grouping processes
Taxonomy Structure for Concurrent Grouping
1.1 Blend
1.1.1 Timbral augmentation
Sustained
Stable
Transforming
Punctuated
1.1.2 Timbral emergence
Sustained
Stable
Transforming
Punctuated
1.2 Non-blend
1.2.1 Timbral heterogeneity
Sustained
Stable
Transforming
Punctuated
1.1 Blend
Definition: The fusion of different sources of acoustic information into a more or less unified auditory event. It primarily depends on onset synchrony, harmonicity, and the degree of overlap of constituent sound spectra. It is reinforced over time by parallel or similar motion in pitch and dynamics.
1.1.1 Timbral Augmentation
Definition: One sound source is identifiable and dominates the timbral result and is embellished, highlighted or reinforced by one or more other sound sources.
Perceptual description: I perceive a blend, manifesting itself as a timbral augmentation.
Sustained
Definition: A sustained sonority over one or more events in which one sound source dominates and is identifiable.
Stable
Definition: A given sound source dominates throughout the duration of the passage.
Perceptual description: I perceive a blend, manifesting itself as a timbral augmentation. The event involved is sustained, and the instruments involved are stable.
Transforming
Definition: The dominating sound source or the embellishing sound source(s) change progressively over the duration of the passage.
Perceptual description: I perceive a blend, manifesting itself as a timbral augmentation. The event involved is sustained, and the instruments involved are transforming.
Punctuated
Definition: A sonority of fairly short duration in which one sound source dominates.
Perceptual description: I perceive a blend, manifesting itself as a timbral augmentation. The event involved is punctuated.
1.1.2 Timbral Emergence
Definition: Timbral emergence is defined as the synthesis of a new timbre, where one cannot identify any of the constituent timbres. Two or more sound sources blend together, none is clearly dominant, and a new timbre emerges.
Perceptual description: I perceive a blend, manifesting itself as a timbral emergence.
Sustained
Definition: A sustained sonority over one or more events in which one sound source dominates and is identifiable.
Stable
Definition: Timbral emergence is defined as the synthesis of a new timbre, where one cannot identify any of the constituent timbres.
Perceptual description: I perceive a blend, manifesting itself as a timbral emergence. The event involved is sustained, and the instruments involved are stable.
Transforming
Definition: The instrumentation changes progressively over the duration of the passage.
Perceptual description: I perceive a blend, manifesting itself as a timbral emergence. The event involved is sustained, and the instruments involved are transforming.
Punctuated
Definition: A sonority of fairly short duration in which sound sources are not easily identifiable.
Perceptual description: I perceive a blend, manifesting itself as a timbral emergence. The event involved is punctuated.
1.2 Non-blend
Definition: Simultaneous sounds that are heard independently.
1.2.1 Timbral Heterogeneity
Definition: Limited to cases in which onset synchrony, harmonicity, and (for continuous cases) parallel motion in pitch and dynamics are present, but the timbres of the sound sources or groups of blended sound sources remain independent due to their timbral dissimilarity.
Perceptual description: I perceive no blend, manifesting itself as a timbral heterogeneity.
Sustained
Definition: A sustained sonority over one or more events in which different sound sources or groups of sound sources are easily distinguished.
Stable
Definition: The instrumentation remains constant throughout the duration of the passage.
Perceptual description: I perceive no blend, manifesting itself as a timbral heterogeneity. The event involved is sustained, and the instruments involved are stable.
Transforming
Definition: The instrumentation changes progressively over the duration of the passage, maintaining separation.
Perceptual description: I perceive no blend, manifesting itself as a timbral heterogeneity. The event involved is sustained, and the instruments involved are transforming.
Punctuated
Definition: A sonority of fairly short duration in which different sound sources or groups of sound sources are easily distinguished.
Perceptual description: I perceive no blend, manifesting itself as a timbral heterogeneity. The event involved is punctuated.
2. Sequential Grouping
Definition: Sequential grouping involves the perceptual connecting of a succession of similar events and the separation of events with different perceptual qualities into distinct groups.
Perceptual organization connects similar sounds into auditory streams
Spectral continuity (pitch and timbre)
Loudness continuity
Spatial continuity
Therefore, timbral differentiation can cause stream segregation and timbral similarity promotes stream integration (McAdams & Bregman, 1979)
The degree of differentiation can be predicted from timbre space distances (Iverson, 1995; Bey & McAdams, 2003)
Taxonomy Structure for Sequential Grouping
2. Sequential grouping
2.1 Integration
2.1.1 Stream
Stable
Transforming
2.1.2 Surface texture
Stable
Transforming
2.2 Segregation
2.2.1 Streams
Stable
Transforming
2.2.2 Stratification
Stable
Transforming
Structure of taxonomic categories in Sequential Grouping
2.1 Integration
Definition: The grouping over time of events into streams or surface textures.
2.1.1 Stream
Definition: A sequence of events produced by a single sound source or groups of blended sound sources are perceived as connected and form a unitary musical pattern.
Perceptual description: I perceive an integration, manifesting itself as a stream.
Stable
Definition: A stream of events played by the same sound source or group of blended sound sources.
Perceptual description: I perceive an integration, manifesting itself as a stream. The event involved is sustained, and the instruments involved are stable.
Transforming
Definition: A stream of events in which the sound source or group of blended sound sources changes over the passage (e.g., Klangfarbenmelodie).
Perceptual description: I perceive an integration, manifesting itself as a stream. The event involved is sustained, and the instruments involved are transforming.
2.1.2 Surface Texture (Textural Integration)
Definition: Overlapping sequences of notes by two or more sound sources, often with distinct rhythmic patterns but in similar registers, which do not form a single stream but are difficult to separately follow through time, and thus form a looser grouping into a surface texture. The term "texture" is used here in its meaning of "the consistency of a surface."
Perceptual description: I perceive an integration, manifesting itself as a surface texture.
Stable
Definition: The sound sources forming the surface texture remain constant over the duration of the passage.
Perceptual description:I perceive an integration, manifesting itself as a surface texture. The event involved is sustained, and the instruments involved are stable.
Transforming
Definition: The sound sources forming the surface texture change over the duration, maintaining the textural integration.
Perceptual description: I perceive an integration, manifesting itself as a surface texture. The event involved is sustained, and the instruments involved are transforming.
2.2 Segregation
Definition: The grouping over time of events into streams or surface textures.
2.2.1 Streams / Segregation
Definition: Multiple independent auditory streams with equivalent prominence. Note that each stream is integrated but segregated from other streams.
Perceptual description: I perceive a segregation, manifesting itself as independent auditory streams.
Stable
Definition: The sound sources forming the separate streams remain constant over the duration of the passage.
Perceptual description: I perceive a segregation, manifesting itself as independent auditory streams. The event involved is sustained, and the instruments involved are stable.
Transforming
Definition: The sound sources forming each separate stream change over the duration of the passage.
Perceptual description: I perceive a segregation, manifesting itself as independent auditory streams. The event involved is sustained, and the instruments involved are transforming.
2.2.2 Stratification
Definition: Orchestral stratification involves looser groupings of events into strata of different prominence (e.g., foreground, middleground, background). A stratum may contain one or more streams, a surface texture, or more loosely grouped collections of instruments that are still distinct from other layers.
Perceptual description: I perceive a segregation, manifesting itself as a stratification.
Stable
Definition: The sound sources grouped into the various strata remain constant over the duration of the passage.
Perceptual description: I perceive a segregation, manifesting itself as a stratification. The event involved is sustained, and the instruments involved are stable.
Transforming
Definition: The sound sources grouped into the various strata change over the duration of the passage.
Perceptual description: I perceive a segregation, manifesting itself as a stratification. The event involved is sustained, and the instruments involved are transforming.
3. Segmental Grouping
Definition: Timbral contrasts form segments as small as melodic-rhythmic patterns and as large as sections of a piece. Contrasts of lesser strength may just highlight changes in other musical parameters and stronger contrasts can create boundaries between adjacent musical materials.
Any kind of acoustic discontinuity can provoke segmentation, including timbral discontinuity
Deliège (1987) – changes in timbre cause segmentation (chunking) of sequences
Deliège (1989) – large-scale sections in music are formed on the basis of similarities in register, texture and instrumentation (i.e., timbre)
Therefore, timbre change ➔ boundary creation and timbre similarity ➔ chunking of events into coherent units
3. Segmental grouping
3.1.1 Antiphonal contrasts
3.1.2 Timbral echoes
3.1.3 Timbral shifts
3.1.4 General contrasts
3.1.5 Sectional boundaries
3.2.1 Orchestral gestures
Structure of taxonomic categories in Segmental Grouping
3.1 Timbral Contrasts
Definition: Timbral contrasts form segments as small as melodic-rhythmic patterns and as large as sections of a piece. Contrasts of lesser strength may just highlight changes in other musical parameters and stronger contrasts can create boundaries between adjacent musical materials.
Perceptual description: I perceive a timbral contrast.
3.1.1 Timbral Shifts
Definition: A kind of orchestral hot potato in which a musical pattern is reiterated with varying orchestrations of similar prominence presented in discrete timbral steps.
Perceptual description: I perceive a timbral contrast, manifesting itself as a timbral shift. The event involved is sustained, and the instruments involved are transforming.
3.1.2 Timbral Echo
Definition: Repetition of a musical pattern by a different sound source or combination of sound sources with timbres that mimic being more distant than the original presentation. At times achieved with off-stage instruments.
Perceptual description: I perceive a timbral contrast, manifesting itself as a timbral echo. The event involved is sustained, and the instruments involved are transforming.
3.1.3 Timbral Juxtaposition
Definition: Musical patterns that are of similar perceptual prominence are set against one another sequentially with different instrumentations.
Perceptual description: I perceive a timbral contrast, manifesting itself as a timbral juxtaposition. The event involved is sustained, and the instruments involved are transforming.
3.1.4 Antiphonal Contrasts
Definition: Timbral contrasts underscoring an alternating call-and-response pattern.
Perceptual description: I perceive a timbral contrast, manifesting itself as an antiphonal contrast. The event involved is sustained, and the instruments involved are transforming.
3.1.5 Sectional Boundaries
Definition: Creation of boundaries of larger-scale sections with strong contrasts in register, texture, and instrumentation.
Perceptual description: I perceive a timbral contrast, manifesting itself as a sectional boundary. The event involved is sustained, and the instruments involved are transforming.
3.2 Timbral Progression
Definition: Timbral progressions over longer timespans can be used to create coherence and dramatic shape within larger-scale formal units.[There is only one subcategory (orchestral gestures) for the moment, leaving open the possibility to add others later.]
3.2.1 Orchestral Gestures
Definition: Large-scale, goal-directed timbral shaping that coordinates various musical elements in order to create a sense of agency and emotional force. Defined in terms of rate of change in instrumentation (gradual vs. sudden) and the direction of change (additive vs. reductive).
Goodchild (2016) proposed a typology of orchestral gestures defined by large-scale changes in instrumentation over time based on time course (either gradual or sudden change) and direction (either additive or reductive changes).
Each gesture adds or removes instruments, gradually or suddenly, as a coordinated process over time.
Due to the combination of instrumental texture, dynamics, tempo and other dimensions, these orchestral gestures can give rise to strong emotional experiences.
Orchestral gestures have a goal-directed sense of motion that plays structural and expressive role on the musical experience as carriers of emotional force.
Gradual gestures are characterized by a sense of developing orchestral growth or progressive abatement.
The sudden gestures represent a rhetorical shift within the musical processes at hand. Sudden change in texture and timbre marks a dramatic turning point.
3.2.1.1 Gradual Addition
Definition: Gradual accumulation of sound source forces over a long timespan within a larger-scale unit.
3.2.1.2 Sudden Addition
Definition: Sudden addition of instrumental forces linking a timespan of lesser to one of greater number of sound sources within a larger-scale unit.
3.2.1.3 Gradual Reduction
Definition: Gradual decrease of sound source forces over a long timespan within a larger-scale unit.
3.2.1.4 Sudden Reduction
Definition: Sudden reduction of instrumental forces linking a timespan of greater to one of lesser number of sound sources within a larger-scale unit.