Download Model Bending: Teaching Circuit Models New Tricks
A technique is introduced for generating novel signal processing systems grounded in analog electronic circuits, called model bending. By applying the ideas behind circuit bending to models of nonlinear analog circuits it is possible to create novel nonlinear signal processors which mimic the behavior of analog electronics, but which are not possible to implement in the analog realm. The history of both circuit bending and circuit modeling is discussed, as well as a theoretical basis for how these approaches can complement each other. Potential pitfalls to the practical application of model bending are highlighted and suggested solutions to those problems are provided, with examples.
Download Virtual Analog Modeling of Distortion Circuits Using Neural Ordinary Differential Equations
Recent research in deep learning has shown that neural networks can learn differential equations governing dynamical systems. In this paper, we adapt this concept to Virtual Analog (VA) modeling to learn the ordinary differential equations (ODEs) governing the first-order and the second-order diode clipper. The proposed models achieve performance comparable to state-of-the-art recurrent neural networks (RNNs) albeit using fewer parameters. We show that this approach does not require oversampling and allows to increase the sampling rate after the training has completed, which results in increased accuracy. Using a sophisticated numerical solver allows to increase the accuracy at the cost of slower processing. ODEs learned this way do not require closed forms but are still physically interpretable.
Download A Virtual Analog Model of the Edp Wasp VCF
In this paper we present a virtual analog model of the voltagecontrolled filter used in the EDP Wasp synthesizer. This circuit is an interesting case study for virtual analog modeling due to its characteristic nonlinear and highly dynamic behavior which can be attributed to its unusual design. The Wasp filter consists of a state variable filter topology implemented using operational transconductance amplifiers (OTAs) as the cutoff-control elements and CMOS inverters in lieu of operational amplifiers, all powered by a unipolar power supply. In order to accurately model the behavior of the circuit we propose extended models for its nonlinear components, focusing particularly on the OTAs. The proposed component models are used inside a white-box circuit modeling framework to create a digital simulation of the filter which retains the interesting characteristics of the original device.
Download Modeling and Extending the Rca Mark Ii Sound Effects Filter
We have analyzed the Sound Effects Filter from the one-of-a-kind RCA Mark II sound synthesizer and modeled it as a Wave Digital Filter using the Faust language, to make this once exclusive device widely available. By studying the original schematics and measurements of the device, we discovered several circuit modifications. Building on these, we proposed a number of extensions to the circuit which increase its usefulness in music production.
Download Analysis of Musical Dynamics in Vocal Performances Using Loudness Measures
In addition to tone, pitch and rhythm, dynamics is one of the expressive dimensions of the performance of a music piece that has received limited attention. While the usage of dynamics may vary from artist to artist, and also from performance to performance, a systematic methodology to automatically identify the dynamics of a performance in terms of musically meaningful terms like forte, piano may offer valuable feedback in the context of music education and in particular in singing. To this end, we have manually annotated the dynamic markings of commercial recordings of popular rock and pop songs from the Smule Vocal Balanced (SVB) dataset which will be used as reference data. Then as a first step for our research goal, we propose a method to derive and compare singing voice loudness curves in polyphonic mixtures. Towards measuring the similarity and variation of dynamics, we compare the dynamics curves of the SVB renditions with the one derived from the original songs. We perform the same comparison using professionally produced renditions from a karaoke website. We relate high values of Spearman correlation coefficient found in some select student renditions and the professional renditions with accurate dynamics.
Download Antiderivative Antialiasing with Frequency Compensation for Stateful Systems
Employing nonlinear functions in audio DSP algorithms requires attention as they generally introduce aliasing. Among others, antiderivative antialiasing proved to be an effective method for static nonlinearities and gave rise to a number of variants, including our AA-IIR method. In this paper we introduce an improvement to AA-IIR that makes it suitable for use in stateful systems. Indeed, employing standard antiderivative antialiasing techniques in such systems alters their frequency response and may cause stability issues. Our method consists in cascading a digital filter after the AA-IIR block in order to fully compensate for unwanted delay and frequency-dependent effects. We study the conditions for such a digital filter to be stable itself and evaluate the method by applying it to the diode clipper circuit.
Download A Quaternion-Phase Oscillator
An approach to designing dynamical systems with a three-dimensional state space is described that can be used to build a variety of non-periodic oscillators. The state space is taken to be a 3sphere, which is identified with the manifold of unit quaternions. Any such system can be described as a quaternion-valued ordinary differential equation, which is digitally realized using an approximation as a finite difference e quation. Two examples are shown. Compared to previous applications of dynamical systems used to generate audio samples, the approach described here offers a wide choice of specific flows which can neither diverge nor approach a stable limit point.
Download Deforming the Oscillator: Iterative Phases Over Parametrizable Closed Paths
Iterative phase formulations allow for the generalization of many oscillatory sound synthesis methods from circles to general parametrizable loops, with or without explicit geometric contexts. This paper describes this approach, leading to the ability to perform modulation, feedback and chaotic oscillations over deformed circles that can include ill-behaved geometries, while allowing modulations or feedback to be deformed as well.
Download Continuous State Modeling for Statistical Spectral Synthesis
Continuous State Markovian Spectral Modeling is a novel approach for parametric synthesis of spectral modeling parameters, based on the sines plus noise paradigm. The method aims specifically at capturing shimmer and jitter - micro-fluctuations in the partials’ frequency and amplitude trajectories, which are essential for the timbre of musical instruments. It allows for parametric control over the timbral qualities, while removing the need for the more computationally expensive and restrictive process of the discrete state space modeling method. A qualitative comparison between an original violin sound and a re-synthesis shows the ability of the algorithm to reproduce the micro-fluctuations, considering their stochastic and spectral properties.
Download Subjective Evaluation of Sound Quality and Control of Drum Synthesis with Stylewavegan
In this paper we investigate into perceptual properties of StyleWaveGAN, a drum synthesis method proposed in a previous publication. For both, the sound quality as well as the control precision StyleWaveGAN has been shown to deliver state of the art performance for quantitative metrics (FAD and MSE of the control parameters). The present paper aims to provide insight into the perceptual relevance of these results. Accordingly, we performed a subjective evaluation of the sound quality as well as a subjective evaluation of the precision of the control using timbre descriptors from the AudioCommons toolbox. We evaluate the sound quality with mean opinion score and make measurements of psychophysical response to the variations of the control. By means of the perceptual tests, we demonstrate that StyleWaveGAN produces better sound quality than state-of-the-art model DrumGAN and that the mean control error is lower than the absolute threshold of perception at every point of measurement used in the experiment.