Real-time Fourier synthesis of ensembles with timbral interpolation

In Fourier synthesis, natural musical sounds are produced by summing time-varying sinusoids. Sounds are analyzed to find the amplitude and frequency characteristics for their sinusoids; interpolation between the characteristics of several sounds is used to produce intermediate timbres. An ensemble can be synthesized by summing all the sinusoids for several sounds, but in practice it is difficult to perform such computations in real time. To solve this problem on inexpensive hardware, it is useful to take advantage of the masking effects of the auditory system. By avoiding the computations for perceptually unimportant sinusoids, and by employing other computation reduction techniques, a large ensemble may be synthesized in real time on the Platypus signal processor. Unlike existing computation reduction techniques, the techniques described in this thesis do not sacrifice independent fine control over the amplitude and frequency characteristics of each sinusoid.U of I OnlyETDs are only available to UIUC Users without author permissio

Machine Tongues XVI: Genetic Algorithms and Their Application to FM Matching Synthesis

Historically, frequency modulation (FM) synthesis has required trial and error to create emulations of natural sounds. This article presents a genetic-algorithm-based technique which determines optimized parameters for reconstruction through FM synthesis of a sound having harmonic partials. We obtain the best results by using invariant modulation indices and a multiple carrier formant FM synthesis model. We present our results along with extensions and generalizations of the technique

A New Algorithm For Bandwidth Association In Bandwidth-Enhanced Additive Sound Modeling

The Bandwidth-Enhanced Additive Model represents sound as a collection of partials having sinusoidal and noise-like characteristics. Bandwidth Association is the process of constructing the bandwidth envelopes for partials in the bandwidth-enhanced model by associating noise energy not captured by conventional sinusoidal modeling processes. We present analytical methods for collecting and associating noise energy by extracting additional information from the short-time analysis spectra. 1. NOISE IN SINUSOIDAL MODELS In representations derived from purely sinusoidal analyses, sounds are described by a collection of sinusoidal components called partials. Sinusoidal partials are defined by time-varying amplitude and frequency envelopes formed by linking spectral energy peaks extracted from short-time Fourier spectra [1, 2, 3]. For sounds that are locally nearly periodic, having very highly concentrated shorttime spectral energy, a perceptually complete representation can be constructed ..

Lemur -- A Tool for Timbre Manipulation

We will present Lemur, a system for generating and manipulating sinusoidal models for sampled sound, implemented as a Macintosh program. Our system uses an enhanced McAulay-Quatieri (MQ) style analysis for modeling sampled sounds. The system provides tools for time and frequency scale modifications, partial editing and pruning, timbre morphing, and many other manipulations in the model domain. Time-variant manipulations may be performed using control files. Third-party implementations of the Lemur model will be discussed. A real-time controllable implementation of a bandwidth-enhanced synthesis algorithm will be demonstrated

Methods for Multiple Wavetable Synthesis of Musical Instrument Tones

Spectrum matching of musical instrument tones is a fundamental problem in computer music. Two methods are presented for determining near-optimal parameters for the synthesis of harmonic musical instrument or voice sounds using the addition of several fixed wavetables with time-varying weights. The overall objective is to find wavetable spectra and associated amplitude envelopes which together provide a close fit to an original time-varying spectrum. Techniques used for determining the wavetable spectra include a genetic algorithm (GA) and principal components analysis (PCA). In one study a GA was used to select spectra from the original signal at various time points. In another study PCA was used to obtain a set of orthogonal basis spectra for the wavetables. In both cases, least-squares solution is utilized to determine the associated amplitude envelopes. Both methods provide solutions which converge gracefully to the original as the number of tables is increased, but three to five wavetables frequently yield a good replica of the original sound. For the three instruments we analyzed, a trumpet, a guitar, and a tenor voice, the GA method seemed to offer the best results, especially when less than four wavetables were used. Comparative results using the methods are discussed and illustrated