In the most general form, the frequency of each non-harmonic partial is a non-negative function of time, In this broad sense, pipe organs, which also have pipes producing non-sinusoidal waveforms, can be considered as a variant form of additive synthesizers.
Summation of principal components and Walsh functions have also been classified as additive synthesis.
"middle C is 261.6 Hz"), In other words, the fundamental frequency alone is responsible for the pitch of the note, while the overtones define the timbre of the sound.
The overtones of a piano playing middle C will be quite different from the overtones of a violin playing the same note; that's what allows us to differentiate the sounds of the two instruments.
(See also Dynamic timbres) Later, in early 1980s, listening tests were carried out on synthetic speech stripped of acoustic cues to assess their significance.
Time-varying formant frequencies and amplitudes derived by linear predictive coding were synthesized additively as pure tone whistles. These methods are characterized by extraction and recomposition of a set of significant spectral peaks corresponding to the several resonance modes occurred in the oral cavity and nasal cavity, in a viewpoint of acoustics.
When humans hear these frequencies simultaneously, we can recognize the sound. water splashing, leaves rustling, etc.) and for "musical sounds" (e.g. This set of parameters (frequencies, their relative amplitudes, and how the relative amplitudes change over time) are encapsulated by the timbre of the sound.
Fourier analysis is the technique that is used to determine these exact timbre parameters from an overall sound signal; conversely, the resulting set of frequencies and amplitudes is called the Fourier series of the original sound signal.
By careful consideration of the DFT frequency-domain representation it is also possible to efficiently synthesize sinusoids of arbitrary frequencies using a series of overlapping frames and the inverse Fast Fourier transform.
It is possible to analyze the frequency components of a recorded sound giving a "sum of sinusoids" representation.