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A synthesizer (spelling var. synthesiser) is an electronic musical instrument designed to produce artificially generated sound, using techniques such as additive, subtractive, FM, physical modelling synthesis, or phase modulation to create sounds.
Synthesizers create sounds through direct manipulation of electrical currents (as in analog synthesizers), mathematical manipulation of discrete values using computers (as in software synthesizers), or by a combination of both methods. In the final stage of the synthesizer, electrical currents are used to cause vibrations in the diaphragms of loudspeakers, headphones, etc. This synthesized sound is contrasted with recording of natural sound, where the mechanical energy of a sound wave is transformed into a signal which will then be converted back to mechanical energy on playback (though sampling significantly blurs this distinction).
The term " speech synthesizer" is also used in electronic speech processing, often in connection with vocoders.
When natural tonal instruments' sounds are analyzed in the frequencyFrequency is the measurement of the number of times that a repeated event occurs per unit time. To calculate the frequency, one fixes a time interval, counts the number of occurrences of the event within that interval, and then divides this count by the l domain, the spectraThe noun spectrum (plural: spectra has a variety of meanings. Ghosts Originally a spectrum was what is now called a spectre, i. a phantom or apparition. Spectral evidence is testimony about what was done by spectres of persons not present physically, or h of tonal instruments exhibit amplitude peaks at the harmonicsThis article is about the harmonic series in music theory. See harmonic series (mathematics) for the related mathematical concept. Pitched musical instruments are usually based on some sort of harmonic oscillator, for example a string or a column of air,. These harmonics' frequencies are primarily located close to the integer multiples of the tone's fundamental frequencyThe fundamental tone often referred to simply as the fundamental is the lowest frequency in a harmonic series. The fundamental frequency of a periodic signal is the inverse of the pitch period length. The pitch period is, in turn, the smallest repeating u.
PercussivePercussion instruments are played by being struck or shaken. They are perhaps the oldest form of musical instruments. Some percussion instruments play not only rhythm, but also melody and harmony. Classifications Most percussion instruments have a distincs and rasps usually lack harmonics, and exhibit spectra that are comprised mainly of noise shaped by the resonant frequencies of the structures that produce the sounds. The resonant properties of the instruments (the spectral peaks of which are also referred to as formantA formant is a preferred resonating frequency of any acoustical system. It is most commonly invoked in phonetics or acoustics as the preferred vibrations of vocal tracts or musical instruments. However, it is equally valid to talk about the formant freques) also shape the spectra of string, wind, voice and other natural instruments.In most conventional synthesizers, for purposes of resynthesis, recordings of real instruments can be thought to be composed of several components.
These component sounds represent the acoustic responses of different parts of the instrument, the sounds produced by the instrument during different parts of a performance, or the behaviour of the instrument under different playing conditions (pitch, intensity of playing, fingering, etc...) The distinctive timbre, intonation and attack of a real instrument can therefore be created by mixing together these components in such a way as resembles the natural behaviour of the real instrument. Nomenclature varies by synthesizer methodology and manufacturer, but the components are often referred to as oscillators or partials. A higher fidelity reproduction of a natural instrument can typically be achieved using more oscillators, but increased computational power and human programming is required, and most synthesizers use between one and four oscillators by default.
Schematic of ADSR One of the most salient aspects of any sound is its amplitude envelope. This envelope determines whether the sound is percussive, like a snare drum, or persistent, like a violin string. Most often, this shaping of the sound's amplitude profile is realized with an " ADSR" (Attack Decay Sustain Release) envelope model applied to control oscillator volumes. Each of these stages is modelled by a change in volume (typically exponential). The attack is the initial run-up of the sound level. The decay is the run down immediately after the attack. Sustain is the volume when the note is held. The release is the volume profile when the note is released. Exponential rates are commonly used because they closely model real physical vibrations, which usually rise or decay exponentially.
Although the oscillations in real instruments also change frequency, most instruments other than the viol-family and human voice can be modelled well without this refinement. This refinement is necessary to generate a vibrato.
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