Spectromorphology is the perceived sonic footprint of a sound spectrum as it manifests in time

Time

Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

. A descriptive spectromorphological analysis of sound is sometimes used in the analysis of electroacoustic music

Electroacoustic music

Electroacoustic music originated in Western art music during its modern era following the incorporation of electric sound production into compositional practice. The initial developments in electroacoustic music composition during the mid-20th century are associated with the activities of composers...

, especially acousmatic music

Acousmatic music

Acousmatic music is a form of electroacoustic music that deals specifically with acousmatic sound as a compositional resource. The practice has a historical basis in musique concrète. It can be created using non-acoustic technology, exists only in a recorded format , and is composed for reception...

. The term was coined by Denis Smalley

Denis Smalley

Denis Arthur Smalley is a composer of electroacoustic music, with a special interest in acousmatic music.-Biography:...

 in 1986 and is considered the most adequate English term to designate the field of sound research associated with the French writer, composer, and academic, Pierre Schaeffer

Pierre Schaeffer

Pierre Henri Marie Schaeffer was a French composer, writer, broadcaster, engineer, musicologist and acoustician of the 20th century. His innovative work in both the sciences —particularly communications and acoustics— and the various arts of music, literature and radio presentation after the end...

.

Schaeffer's work at INA/GRM in Paris, beginning in the late 1940s, culminated in the publication of the book Traité des objets musicaux in 1966. Smalley's notion of spectromorphology builds upon Schaeffer's theories relating to the use of a classification system for various categories of sound .

Smalley's term refers to the descriptive analysis of perceived morphological developments in sound spectra over time, and it implies that the "spectro" cannot exist without the morphology

Morphological typology

Morphological typology is a way of classifying the languages of the world that groups languages according to their common morphological structures. First developed by brothers Friedrich von Schlegel and August von Schlegel, the field organizes languages on the basis of how those languages form...

: something has to be shaped and that something must have sonic content (Smalley, 1986, 1997).

Theoretical framework

The theoretical framework of spectro-morphology is articulated mainly in four parts:

• the typology
  Typology
  Typology is the study of types. More specifically, it may refer to:*Typology , division of culture by races*Typology , classification of things according to their characteristics...
  
   of the spectra
• morphology
• motion
• structuring processes.

Spectral typologies

Smalley defines three different spectral typologies that exist in what he calls the noise-note continuum

Continuum (theory)

Continuum theories or models explain variation as involving a gradual quantitative transition without abrupt changes or discontinuities. It can be contrasted with 'categorical' models which propose qualitatively different states.-In physics:...

. This continuum is subdivided into three principal elements:

• the noise.
• the node (an event having a more complex texture than a single pitch).
• the note, which is in turn subdivided into note, harmonic spectrum and inharmonic spectrum.

Morphological archetypes

Smalley also designates different morphological archetype

Archetype

An archetype is a universally understood symbol or term or pattern of behavior, a prototype upon which others are copied, patterned, or emulated...

s:

• attack-impulse. Modeled on the single detached note: a sudden onset which is immediately terminated. In this instance the attack-onset is also the termination.
• attack-decay (closed and open) - modeled on sounds in which the attack-onset is extended by a resonance
  Resonance
  In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
  
   that quickly or gradually decays towards termination. The closed form represents a quick decay which is strongly attack-determined. The open form reflects a more gradual decay where the ear is drawn away from the formative influence of the attack into the continuing behaviour of the sound on its way to termination.
• graduated continuant - Modeled on sustained sounds. The onset is graduated, settling into a continuant
  Continuant
  A continuant is a sound produced with an incomplete closure of the vocal tract. That is, any sound except a stop or nasal. An affricate is considered to be a complex segment, composed of both a stop and a continuant.-See also:...
  
  phase which eventually closes in a graduated termination. The onset is perceived as a much less formative influence than in the other two archetypes. Attention is drawn to the way in which the sound is maintained rather than to its initiation.