A Tutorial on Spectral Sound Processing Using Max/MSP and Jitter
J F Charles · Computer Music Journal · 2008
For computer musicians, sound processing in the frequency domain is an important and widely used technique.Two particular frequency-domain tools of great importance for the composer are the phase vocoder and the sonogram.The phase vocoder, an analysis-resynthesis tool based on a sequence of overlapping short-time Fourier transforms, helps perform a variety of sound modifications, from time stretching to arbitrary control of energy distribution through frequency space.The sonogram, a graphical representation of a sound's spectrum, offers composers more readable frequency information than a time-domain waveform.Such tools make graphical sound synthesis convenient.A history of graphical sound synthesis is beyond the scope of this article, but a few important figures include Evgeny Murzin, Percy Grainger, and Iannis Xenakis.In 1938, Evgeny Murzin invented a system to generate sound from a visible image; the design, based on the photo-optic sound technique used in cinematography, was implemented as the ANS synthesizer in 1958 (Kreichi 1995).Percy Grainger was also a pioneer with the "Free Music Machine" that he designed and built with Burnett Cross in 1952 (Lewis 1991); the device was able to generate sound from a drawing of an evolving pitch and amplitude.In 1977, Iannis Xenakis and associates built on these ideas when they created the famous UPIC (Unit é Polyagogique Informatique du CEMAMu; Marino, Serra, and Raczinski 1993).In this article, I explore the domain of graphical spectral analysis and synthesis in real-time situations.The technology has evolved so that now, not only can the phase vocoder perform analysis and synthesis in real time, but composers have access to a new conceptual approach: spectrum modifications considered as graphical processing.Nevertheless, the underlying matrix representation is still intimidating to many musicians.Consequently, the musical potential of this technique is as yet unfulfilled.