Download Adaptive FM Synthesis This article describes an adaptive synthesis technique based on frequency (phase) modulation of arbitrary input signals. The background and motivation for the development of the technique, as well as related work, are discussed. A detailed description of delay line-based phase modulation of sinusoidal and complex signals is provided. The basic design of an implementation of the technique is presented and commented. A series of examples using four different instrumental sources are discussed. The results show a wide range of possible effects through the use of the technique, from addition of higher components, to changes in the odd-even harmonic balance and the introduction of controlled inharmonicity.
Download Modal Distribution Synthesis from Sub-Sampled Autocorrelation Function The problem of signal synthesis from bilinear time-frequency representations such as the Wigner distribution has been investigated [1,2,4] using methods which exploit an outer-product interpretation of these distributions. The Modal distribution is a timefrequency distribution specifically designed to model the quasiharmonic, multi-sinusoidal, nature of music signals and belongs to the Cohen general class of time-frequency distributions. Existing methods of synthesis from the Modal distribution [3] are based on a sinusoidal-analysis-synthesis procedure using estimates of instantaneous frequency and amplitude values. In this paper we develop an innovative synthesis procedure for the Modal distribution based on the outer-product interpretation of bilinear timefrequency distributions. We also propose a streaming objectoriented implementation of the resynthesis in the SndObj library [6] based on previous work which implemented a streaming implementation of the Modal distribution [7]. The theoretical background to the Modal distribution and to signal synthesis of Wigner distributions is first outlined followed by an explanation of the design and implementation of the Modal distribution synthesis. Suggestions for future extensions to the synthesis procedure are given.
Download A modified FM synthesis approach to bandlimited signal generation Techniques for the generation of bandlimited signals for application to digital implementations of subtractive synthesis have been researched by a number of authors. This paper hopes to contribute to the variety of approaches by proposing a technique based on Frequency Modulation (FM) synthesis. This paper presents and explains the equations required for bandlimited pulse generation using modified FM synthesis. It then investigates the relationships between the modulation index and the quality of the reproduction in terms of authenticity and aliasing for a sawtooth wave. To determine the performance of this technique in comparison to others two sets of simulation results are offered: the first computes the relative power of the non-harmonic components, and the second uses the Perceptual Evaluation of Audio Quality (PEAQ) algorithm. It is shown that this technique compares well with the alternatives. The paper concludes with suggestions for the direction of future improvements to the method.
Download Asymmetric-spectra methods for adaptive FM synthesis This article provides an overview of further methods for producing hybrid natural-synthetic spectra with adaptive frequency modulation (AdFM). It focuses on three different techniques for the generation of asymmetric spectra based on single-sideband FM, asymmetric FM and Split-sideband synthesis. The first two techniques are applied to the variable delay line implementation of AdFM, whereas the third is based on an extension of the heterodyne method. The article discusses the principles involved in each synthesis technique in good detail, providing one reference implementation for each. A number of examples are discussed, demonstrating the possibilities for a variety of digital audio effects applications.
Download Adaptive Phase Distortion Synthesis This article discusses Phase Distortion synthesis and its application to arbitrary input signals. The main elements that compose the technique are presented. Its similarities to Phase Modulation are discussed and the equivalence between the two techniques is explored. Two alternative methods of distorting the phase of an arbitrary signal are presented. The first is based on the audio-rate modulation of a first-order allpass filter coefficient. The other method relies on a re-casting of the Phase Modulation equation, which leads to a heterodyned form of waveshaping. The relationship of these implementations to the original technique is explored in detail. Complementing the article, a number of examples are discussed, demonstrating the application of the technique as an interesting digital audio effect.
Download Five Variations on a Feedback Theme This is a study on a set of feedback amplitude modulation oscillator equations. It is based on a very simple and inexpensive algorithm which is capable of generating a complex spectrum from a sinusoidal input. We examine the original and five variations on it, discussing the details of each synthesis method. These include the addition of extra delay terms, waveshaping of the feedback signal, further heterodyning and increasing the loop delay. In complement, we provide a software implementation of these algorithms as a practical example of their application and as demonstration of their potential for synthesis instrument design.
Download Handling Inharmonic Series with Median-Adjustive Trajectories A new method for the analysis of inharmonic instrumental tones is presented. The method exploits an equation derived from the well-know inharmonic series equation, where the inharmonicity coefficient is balanced with the frequencies and numbers of any two partials extracted from a pseudo-harmonic series. A serial search for increasingly deviating spectral peaks is aided with the integrated refinement of increasingly reliable inharmonicity coefficient and fundamental frequency estimates. This firsthand approach to the problem of evaluating inharmonic spectra brings about an unprecedented level of simplicity, efficiency and accuracy.
Download A Model of Partial Tracks for Tension-Modulated Steel-String Guitar Tones This paper introduces a spectral model for plucked, steel string tones, based on functional models for time-varying fundamental frequency and inharmonicity coefficient. Techniques to evaluate those analytical values at different time indexes are reviewed and commented. A method to evaluate the unknowns of the fundamental frequency and inharmonicity coefficient functions and match the data of a given tone is presented. Frequency tracks can thereafter be deployed and traced for all values of time. Their accuracy is discussed, and applications for the model are suggested.
Download Digital Emulation of Distortion Effects by Wave and Phase Shaping Methods This paper will consider wave (amplitude) and phase signal shaping techniques for the digital emulation of distortion effect processing. We examine how to determine the Wave- and Phaseshaping functions with harmonic amplitude and phase data. Three distortion effects units are used to provide test data. The action of the Wave- and Phase- shaping functions derived for these effects is demonstrated with the assistance of a superresolution frequency-domain analysis technique.