Realtime Musical Applications using FFT based Resynthesis
Zack Settel, Cort Lippe · University of Michigan Library Repository · 1994
The Fast Fourier Transform (FFT) is a powerful general-purpose algorithm widely used in signal analysis. FFTs are useful when the spectral information of a signal is needed, such as in pitch tracking or vocoding algorithms. The FFT can be combined with the Inverse Fast Fourier Transform (IFFT) in order to resynthesize signals based on its analyses.This application of the FFT/IFFT is of great interest in electro-acoustic music because it allows for a high degree of control of a given signal's spectral information (an important aspect of timbre) allowing for flexible, and efficient implementation of signal processing algorithms. Real-time implementations of the FFT and IFFT are of particular interest since they may be used to provide musicians with highly responsive and straight-forward means for generating and controlling sound in live-performance situations. This paper presents musical applications using the IRCAM Signal Processing Workstation (ISPW) that make use of FFT/IFFT-based resynthesis for timbral transformation in real time. An intuitive and straightforward user interface, intended for use by musicians, has been developed by the authors in the Max programming environment. Techniques for filtering, cross-synthesis, noise reduction, dynamic spectral shaping, and resynthesis are presented along with control structures that allow for fine timbral modification and control of complex sound transformations using few parameters. Emphasis is also placed on developing control structures derived from real-time analyses (time and frequency domain) of a musician's input. The ideas and musical applications, discussed in this paper, offer composers an intuitive approach to timbral transformation in electro-acoustic music, and new possibilities in the domain of live signal processing that promise to be of general interest to musicians.