Timbre
Imagine two musicians playing the exact same note at the exact same volume. A violinist draws a bow across strings while a flutist blows air through a tube. To your ears, these sounds remain distinct despite sharing pitch and loudness. This difference is timbre. It is the attribute that allows you to tell a choir voice from a musical instrument or an oboe from a clarinet. Musicians rely on this quality to distinguish instruments even when they play notes at identical pitch and amplitude levels. The Acoustical Society of America defines it as the attribute enabling a listener to judge that two nonidentical sounds are dissimilar. They specify that timbre depends primarily upon the frequency spectrum, sound pressure, and temporal characteristics.
A spectrogram of the first second of an E9 suspended chord played on a Fender Stratocaster guitar reveals complex waveforms. These waves show how physical characteristics like frequency spectrum and envelope govern the sound. Robert Erickson identified five major acoustic parameters that determine what he called the elusive attributes of timbre. One parameter involves the range between tonal and noiselike character. Another covers the spectral envelope which creates coloration in the sound. Time envelopes describe rise, duration, and decay using the acronym ADSR for attack, decay, sustain, and release. A violinist can change timbre by playing sul tasto to produce a light airy tone or sul ponticello for a harsh aggressive sound. Electric guitarists use effects units and graphic equalizers to alter their tone further.
Hector Berlioz and Richard Wagner made significant contributions to orchestral development during the nineteenth century. Wagner's Sleep motif from Act 3 of his opera Die Walküre passes through a gamut of orchestral timbres. The woodwind section begins with a flute followed by an oboe before the massed strings take over. Finally brass instruments including French horns complete the sequence. Claude Debussy elevated timbre to an unprecedented structural status in works like Prélude à l'après-midi d'un faune where the color of flute and harp functions referentially. Gustav Mahler illustrated this increasing role in his Sixth Symphony Scherzo movement. Norman Del Mar described how Mahler passed repeated notes through a succession of piled octaves that leap-frog with Cs added to As. This passage moves from horns and pizzicato strings through trumpet clarinet flute piccolo and finally oboe.
Listeners can identify an instrument even at different pitches and loudness levels within various environments. Acoustic analysis of the clarinet shows waveforms irregular enough to suggest three instruments rather than one. David Luce suggests certain strong regularities in the acoustic waveform must exist which are invariant with respect to these variables. Robert Erickson argues there are few regularities and they do not explain our powers of recognition and identification. He suggests borrowing the concept of subjective constancy from studies of vision and visual perception. Psychoacoustic experiments from the 1960s onwards tried to elucidate the nature of timbre using multidimensional scaling algorithms. The most consistent outcomes show brightness or spectral energy distribution as important factors. The bite rate and synchronicity rise time of the attack also remain critical for listener identification.
The tristimulus model measures the mixture of harmonics in a given sound grouped into three sections. It reduces dozens or hundreds of sound partials down to only three values. The first tristimulus measures the relative weight of the first harmonic while the second measures the combined weight of the second third and fourth harmonics. The third tristimulus measures the relative weight of all remaining harmonics. Brightness serves as one of the perceptually strongest distinctions between sounds according to researchers. They formalize it acoustically as an indication of the amount of high-frequency content in a sound. This measure uses the spectral centroid to quantify the difference. More evidence and applications would be needed regarding this type of representation to validate it fully.
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Common questions
What is timbre in music?
Timbre is the attribute that allows a listener to judge that two nonidentical sounds are dissimilar despite sharing pitch and loudness. It depends primarily upon the frequency spectrum, sound pressure, and temporal characteristics.
Who defined the five major acoustic parameters of timbre?
Robert Erickson identified five major acoustic parameters that determine what he called the elusive attributes of timbre. These parameters include the range between tonal and noiselike character, the spectral envelope, and time envelopes described by the acronym ADSR for attack, decay, sustain, and release.
How did Hector Berlioz and Richard Wagner contribute to orchestral development regarding timbre?
Hector Berlioz and Richard Wagner made significant contributions to orchestral development during the nineteenth century. Wagner's Sleep motif from Act 3 of his opera Die Walküre passes through a gamut of orchestral timbres including flute, oboe, massed strings, and brass instruments like French horns.
What does the tristimulus model measure in a given sound?
The tristimulus model measures the mixture of harmonics in a given sound grouped into three sections. The first tristimulus measures the relative weight of the first harmonic while the second measures the combined weight of the second third and fourth harmonics and the third measures the relative weight of all remaining harmonics.
When were psychoacoustic experiments conducted to elucidate the nature of timbre?
Psychoacoustic experiments from the 1960s onwards tried to elucidate the nature of timbre using multidimensional scaling algorithms. The most consistent outcomes show brightness or spectral energy distribution as important factors along with bite rate and synchronicity rise time of the attack.